Neoadjuvant atezolizumab for resectable non-small cell lung cancer: an open-label, single-arm phase II trial.

In an ongoing, open-label, single-arm phase II study ( NCT02927301 ), 181 patients with untreated, resectable, stage IB-IIIB non-small cell lung cancer received two doses of neoadjuvant atezolizumab monotherapy. The primary end point was major pathological response (MPR; ≤10% viable malignant cells) in resected tumors without EGFR or ALK alterations. Of the 143 patients in the primary end point analysis, the MPR was 20% (95% confidence interval, 14-28%). With a minimum duration of follow-up of 3 years, the 3-year survival rate of 80% was encouraging. The most common adverse events during the neoadjuvant phase were fatigue (39%, 71 of 181) and procedural pain (29%, 53 of 181), along with expected immune-related toxicities; there were no unexpected safety signals. In exploratory analyses, MPR was predicted using the pre-treatment peripheral blood immunophenotype based on 14 immune cell subsets. Immune cell subsets predictive of MPR in the peripheral blood were also identified in the tumor microenvironment and were associated with MPR. This study of neoadjuvant atezolizumab in a large cohort of patients with resectable non-small cell lung cancer was safe and met its primary end point of MPR ≥ 15%. Data from this single-arm, non-randomized trial suggest that profiles of innate immune cells in pre-treatment peripheral blood may predict pathological response after neoadjuvant atezolizumab, but additional studies are needed to determine whether these profiles can inform patient selection and new therapeutic approaches.

Atezolizumab Treatment of Tumors with High Tumor Mutational Burden from MyPathway, a Multicenter, Open-Label, Phase IIa Multiple Basket Study.

High tumor mutational burden (TMB-H) correlates with improved immunotherapy response. We assessed atezolizumab 1,200 mg every 3 weeks for TMB-H tumors from MyPathway (NCT02091141), a phase IIa multibasket study. One hundred twenty-one patients had advanced solid tumors with TMB ≥10 mut/Mb by any Clinical Laboratory Improvement Amendments (CLIA)-certified assay. The preplanned primary endpoint was objective response rate (ORR) in patients with TMB ≥16 mut/Mb tumors by FoundationOne TMB testing [F1(CDx)]. Patients with F1(CDx) TMB ≥10 and <16 mut/Mb were also evaluated. Ninety patients with 19 tumor types and F1(CDx) TMB ≥10 mut/Mb were efficacy evaluable. In 42 patients with F1(CDx) TMB ≥16 mut/Mb, confirmed ORR was 38.1% [16/42; 95% confidence interval (CI), 23.6-54.4], and disease control rate was 61.9% (26/42; 95% CI, 45.6-76.4) versus 2.1% (1/48; 95% CI, 0.1-11.1) and 22.9% (11/48; 95% CI, 12.0-37.3) for 48 patients with TMB ≥10 and <16 mut/Mb. Responses were observed in nine different tumor types (47%; 9/19). SIGNIFICANCE: Atezolizumab monotherapy had promising, durable clinical activity across a variety of advanced solid tumor types in patients with TMB ≥16 mut/Mb tumors lacking other suitable treatment options and who were immunotherapy-naïve at enrollment, regardless of microsatellite instability status. Limited activity was observed in tumors with TMB ≥10 and <16 mut/Mb. See related commentary by Maron and Klempner, p. 602. This article is highlighted in the In This Issue feature, p. 587.

H3K9me3-heterochromatin loss at protein-coding genes enables developmental lineage specification.

Gene silencing by chromatin compaction is integral to establishing and maintaining cell fates. Trimethylated histone 3 lysine 9 (H3K9me3)-marked heterochromatin is reduced in embryonic stem cells compared to differentiated cells. However, the establishment and dynamics of closed regions of chromatin at protein-coding genes, in embryologic development, remain elusive. We developed an antibody-independent method to isolate and map compacted heterochromatin from low-cell number samples. We discovered high levels of compacted heterochromatin, H3K9me3-decorated, at protein-coding genes in early, uncommitted cells at the germ-layer stage, undergoing profound rearrangements and reduction upon differentiation, concomitant with cell type-specific gene expression. Perturbation of the three H3K9me3-related methyltransferases revealed a pivotal role for H3K9me3 heterochromatin during lineage commitment at the onset of organogenesis and for lineage fidelity maintenance.

Polycomb Repressive Complex 2 Proteins EZH1 and EZH2 Regulate Timing of Postnatal Hepatocyte Maturation and Fibrosis by Repressing Genes With Euchromatic Promoters in Mice.

BACKGROUND & AIMS: Little is known about mechanisms that underlie postnatal hepatocyte maturation and fibrosis at the chromatin level. We investigated the transcription of genes involved in maturation and fibrosis in postnatal hepatocytes of mice, focusing on the chromatin compaction the roles of the Polycomb repressive complex 2 histone methyltransferases EZH1 and EZH2. METHODS: Hepatocytes were isolated from mixed background C57BL/6J-C3H mice, as well as mice with liver-specific disruption of Ezh1 and/or Ezh2, at postnatal day 14 and 2 months after birth. Liver tissues were collected and analyzed by RNA sequencing, H3K27me3 chromatin immunoprecipitation sequencing, and sonication-resistant heterochromatin sequencing (a method to map heterochromatin and euchromatin). Liver damage was characterized by histologic analysis. RESULTS: We found more than 3000 genes differentially expressed in hepatocytes during liver maturation from postnatal day 14 to month 2 after birth. Disruption of Ezh1 and Ezh2 in livers caused perinatal hepatocytes to differentiate prematurely and to express genes at postnatal day 14 that would normally be induced by month 2 and differentiate prematurely. Loss of Ezh1 and Ezh2 also resulted in liver fibrosis. Genes with H3K27me3-postive and H3K4me3-positive euchromatic promoters were prematurely induced in hepatocytes with loss of Ezh1 and Ezh2-these genes included those that regulate hepatocyte maturation, fibrosis, and genes not specifically associated with the liver lineage. CONCLUSIONS: The Polycomb repressive complex 2 proteins EZH1 and EZH2 regulate genes that control hepatocyte maturation and fibrogenesis and genes not specifically associated with the liver lineage by acting at euchromatic promoter regions. EZH1 and EZH2 thereby promote liver homeostasis and prevent liver damage. Strategies to manipulate Polycomb proteins might be used to improve hepatocyte derivation protocols or developed for treatment of patients with liver fibrosis.

Brachypodium distachyon line Bd3-1 resistance is elicited by the barley stripe mosaic virus triple gene block 1 movement protein.

Barley stripe mosaic virus North Dakota 18 (ND18), Beijing (BJ), Xinjiang (XJ), Type (TY) and CV21 strains are unable to infect the Brachypodium distachyon Bd3-1 inbred line, which harbours a resistance gene designated Bsr1, but the Norwich (NW) strain is virulent on Bd3-1. Analysis of ND18 and NW genomic RNA reassortants and RNAß mutants demonstrates that two amino acids within the helicase motif of the triple gene block 1 (TGB1) movement protein have major effects on their Bd3-1 phenotypes. Resistance to ND18 correlates with an arginine residue at TGB1 position 390 (R(390)) and a threonine at position 392 (T(392)), whereas the virulent NW strain contains lysines (K) at both positions. ND18 TGB1 R390K ((ND)TGB1(R390K)) and (ND)TGB1(T392K) single substitutions, and an (ND)TGB1(R390K,T392K) double mutation resulted in systemic infections of Bd3-1. Reciprocal (ND)TGB1 substitutions into (NW)TGB1 ((NW)TGB1(K390R) and (NW)TGB1(K392T)) failed to affect virulence, implying that K(390) and K(392) compensate for each other. In contrast, an (NW)TGB1(K390R,K392T) double mutant exhibited limited vascular movement in Bd3-1, but developed prominent necrotic streaks that spread from secondary leaf veins. This phenotype, combined with the appearance of necrotic spots in certain ND18 mutants, and necrosis and rapid wilting of Bd3-1 plants after BJ strain ((BJ)TGB1(K390,T392)) inoculations, show that Bd3-1 Bsr1 resistance is elicited by the TGB1 protein and suggest that it involves a hypersensitive response.