Diffuse pleural mesotheliomas with genomic near-haploidization: a newly recognized subset with distinct clinical, histologic, and molecular features

PURPOSE

Diffuse pleural mesotheliomas (DPMs) with genomic near-haploidization (GNH) represent a novel subtype first recognized by the TCGA project; however, its clinicopathologic and molecular features remain poorly defined.

EXPERIMENTAL DESIGN

We analyzed clinical genomic profiling data from 290 patients with DPM using the MSK-IMPACT assay. Allele-specific copy number analysis was performed using the FACETS algorithm.

RESULTS

210 patients were evaluable for LOH analysis using FACETS. In this cohort, GNH was detected in 10 cases (4.8%). Compared to non-GNH tumors, GNH DPMs were associated with younger age and less frequent self-reported history of occupational asbestos exposure. Histologically, GNH DPMs were enriched in biphasic subtype (80% vs. 14.5%) and showed abundant tumor infiltrating lymphocytes (TILs). Genomic analysis revealed a higher frequency of TP53 alterations, while SETDB1 mutations were present in nearly all and only in this subset. The clinicopathologic and molecular findings were further validated in a separate cohort. Despite the younger age, patients with GNH DPMs had a shorter overall survival (10.9 vs. 25.4 months, p=0.004); the poor prognostic impact of GNH remained significant after controlling for biphasic histology. Out of three patients with GNH DPMs who received immune checkpoint blockade (ICB), two achieved a clinician assessed partial response.

CONCLUSIONS

GNH defines an aggressive subtype of mainly biphasic DPMs in younger patients with recurrent alterations in SETDB1 and TP53. The enrichment in biphasic histology and TILs, together with our preliminary ICB response data and anecdotal clinical trial data, suggests that further evaluation of immunotherapy may be warranted in this subset.

Diffuse Pleural Mesothelioma: Advances in Molecular Pathogenesis, Diagnosis, and Treatment

Diffuse pleural mesothelioma (DPM) is a highly aggressive malignant neoplasm arising from the mesothelial cells lining the pleural surfaces. While DPM is a well-recognized disease linked to asbestos exposure, recent advances have expanded our understanding of molecular pathogenesis and transformed our clinical practice. This comprehensive review explores the current concepts and emerging trends in DPM, including risk factors, pathobiology, histologic subtyping, and therapeutic management, with an emphasis on a multidisciplinary approach to this complex disease.

Plexin B1 controls Treg numbers, limits allergic airway inflammation, and regulates mucins

We investigated the effect of global Plexin B1 deficiency on allergic airway responses to house dust mite (HDM) or ovalbumin (OVA). In the HDM model, there were higher Th2 cytokine levels in the BALF of Plexin B1 knock-out (KO) mice compared to wild type (WT), and tissue inflammation and mucus production were modestly enhanced. In the OVA model, Plexin B1 deficiency led to increases in lung inflammation, mucus production, and lung Th2 cytokines accompanied by dysregulated mucin gene expression without affecting anti-OVA IgE/IgG1 levels. Spleen cells from Plexin B1 KO mice proliferated more robustly than WT cells in vitro to a variety of stimuli. Plexin B1 KO CD4+ T cells from spleens expressed higher levels of Ki-67 and CD69 compared to WT cells. Spleen cells from naïve Plexin B1 KO mice secreted increased amounts of IL-4 and IL-6 when pulsed in vitro with OVA whereas in vivo OVA-primed spleen cells produced IL-4/IL-5 when subjected to in vitro OVA restimulation. The upregulated allergic inflammatory response in Plexin B1 KO mice was associated with a lower number of Tregs in the lung tissues. Moreover, these mice displayed lower numbers of Treg cells in the lymphoid tissues at the baseline. These results demonstrate a previously unrecognized link between Plexin B1, Treg cells, and mucus in allergic lung inflammation.

Targeting NFE2L2/KEAP1 Mutations in Advanced NSCLC With the TORC1/2 Inhibitor TAK-228

INTRODUCTION

Increased insight into the mutational landscape of squamous cell lung cancers (LUSCs) in the past decade has not translated into effective targeted therapies for patients with this disease. NRF2, encoded by NFE2L2, and its upstream regulator, KEAP1, control key aspects of redox balance and are frequently mutated in NSCLCs.

METHODS

Here, we describe the specific potent activity of TAK-228, a TORC1/2 inhibitor, in NSCLC models harboring NRF2-activating alterations and results of a phase 2 clinical trial of TAK-228 in patients with advanced NSCLC harboring NRF2-activating alterations including three cohorts (NFE2L2-mutated LUSC, KEAP1-mutated LUSC, KRAS/NFE2L2- or KEAP1-mutated NSCLC).

RESULTS

TAK-228 was most efficacious in a LUSC cohort with NFE2L2 alterations; the overall response rate was 25% and median progression-free survival was 8.9 months. Additional data suggest that concurrent inhibition of glutaminase with the glutaminase inhibitor CB-839 might overcome metabolic resistance to therapy in these patients.

CONCLUSIONS

TAK-228 has single-agent activity in patients with NRF2-activated LUSC. This study reframes oncogenic alterations as biologically relevant based on their downstream effects on metabolism. This trial represents, to the best of our knowledge, the first successful attempt at metabolically targeting NSCLC and identifies a promising targeted therapy for patients with LUSC, who are bereft of genotype-directed therapies.

Sarcomatoid Mesothelioma with Bland Histologic Features: A Potential Pitfall in Diagnosis

Sarcomatoid mesotheliomas can be challenging to diagnose on small biopsy specimens, where limited material may preclude definitive assessment of invasion and lesional cells can have relatively bland cytology with no mesothelial marker expression. We report a case of a patient who presented with a pleural effusion and had subsequent pleural biopsy that showed a bland, uniform spindle cell proliferation in a mildly myxoid background. There was little if any collagen; no chest wall, soft tissue, or fat; and mesothelial markers were negative. The cells were positive for pancytokeratin and GATA3 by immunohistochemistry, and in situ hybridization showed a "negative" result for homozygous loss of CDKN2A; however, there was partial (heterozygous) loss of one allele. A diagnosis of atypical spindle cell proliferation was made based on these findings. Several months later, the patient had a repeat pleural biopsy that showed spindled cells with more pleomorphism, areas of invasion into the chest wall, and the same partial loss of CDKN2A, consistent with a sarcomatoid mesothelioma. This case underscores the challenges present on small biopsy specimens, the fact that sarcomatoid mesotheliomas can be relatively bland appearing with focal pleomorphism, and that heterozygous loss of CDKN2A should be considered a positive result indicative of a neoplastic process.

Mice Expressing Cosegregating Single Nucleotide Polymorphisms (D298G and N397I) in TLR4 Have Enhanced Responses to House Dust Mite Allergen

Asthma is a common and ubiquitous chronic respiratory disease that is associated with airway inflammation and hyperreactivity resulting in airway obstruction. It is now accepted that asthma is controlled by a combination of host genetics and environment in a rather complex fashion; however, the link between sensing of the environment and development and exacerbation of allergic lung inflammation is unclear. Human populations expressing cosegregating D299G and T399I polymorphisms in the TLR4 gene are associated with a decreased risk for asthma in adults along with hyporesponsiveness to inhaled LPS, the TLR4 ligand. However, these data do not account for other human genetic or environmental factors. Using a novel mouse strain that expresses homologous human TLR4 polymorphisms (TLR4-single nucleotide polymorphism [SNP]), we directly tested the effect of these TLR4 polymorphisms on in vivo responses to allergens using two models of induction. We report that intact TLR4 is required for allergic inflammation when using the OVA and LPS model of induction, as cellular and pathological benchmarks were diminished in both TLR4-SNP and TLR4-deficent mice. However, in the more clinically relevant model using house dust mite extract for induction, responses were enhanced in the TLR4-SNP mice, as evidenced by greater levels of eosinophilic inflammation, Th2 cytokine production, and house dust mite-specific IgG1 production compared with wild-type mice; however, mucus production and airway hyperreactivity were not affected. These results suggest that the TLR4 polymorphic variants (genes) interact differently with the allergic stimulation (environment).

A mouse model of human TLR4 D299G/T399I SNPs reveals mechanisms of altered LPS and pathogen responses

Two cosegregating single-nucleotide polymorphisms (SNPs) in human TLR4, an A896G transition at SNP rs4986790 (D299G) and a C1196T transition at SNP rs4986791 (T399I), have been associated with LPS hyporesponsiveness and differential susceptibility to many infectious or inflammatory diseases. However, many studies failed to confirm these associations, and transfection experiments resulted in conflicting conclusions about the impact of these SNPs on TLR4 signaling. Using advanced protein modeling from crystallographic data of human and murine TLR4, we identified homologous substitutions of these SNPs in murine Tlr4, engineered a knock-in strain expressing the D298G and N397I TLR4 SNPs homozygously, and characterized in vivo and in vitro responses to TLR4 ligands and infections in which TLR4 is implicated. Our data provide new insights into cellular and molecular mechanisms by which these SNPs decrease the TLR4 signaling efficiency and offer an experimental approach to confirm or refute human data possibly confounded by variables unrelated to the direct effects of the SNPs on TLR4 functionality.

Rice body formation due to Haemophilus parainfluenza-associated chronic arthropathy

A 68-year-old woman with a medical history significant for psoriatic arthritis was found to have an enlarged, painful lump on her left hip 15 months after intramedullary rod placement for a left subtrochanteric femur fracture sustained in a fall. Histopathological findings showed rice body formation (RBF) with concurrent H. parainfluenza. RBF is a relatively rare arthropathy of a subset of chronic inflammatory disease such as rheumatoid arthritis or tuberculous arthropathy. RBF associated with psoriatic arthritis or orthopedic hardware placement has been reported in a handful of cases in the literature but there has not been any definitive evidence for RBF as a result of Haemophilus parainfluenza infections and is a rather unusual characteristic of this case.

Gastric AA amyloidosis secondary to chronic infection presenting with hematemesis: a case report

AA amyloidosis, previously known as secondary amyloidosis, has been associated with multiple chronic inflammatory conditions, including various autoimmune diseases and rarely chronic infection. Hereby, we present a case of AA amyloidosis secondary to chronic infection which initially presented with nausea and hematemesis. Endoscopic biopsies revealed diffuse AA amyloid deposition in the stomach, but not the esophagus. AA Amyloidosis presumably compromised gastric motility, promoted reflux related esophageal ulcers and erosions, and caused his cardiac and renal insufficiency. Therefore, endoscopic biopsies could be practical investigation to identify AA amyloidosis in the setting of chronic inflammatory diseases, especially with multi-organ involvement.

Porcelain Heart: A Case of Diffuse Myocardial Calcification

The pathophysiology of myocardial calcifications is variable and may have potentially fatal consequences if undiagnosed and untreated.

Emphysematous gastritis due to Sarcina ventriculi infection in a diabetic liver-kidney transplant recipient

Emphysematous gastritis (EG) is a rare and potentially lethal process caused by invasive, gas-producing bacteria leading to inflammation and gas dissection of the stomach. The most common etiologic agents are Clostridium infections, but other organisms, including enterobacteria, staphylococcus, and fungi have also been identified. We report the first case of EG due to Sarcina ventriculi in a solid organ transplant recipient, who presented with epigastric pain and vomiting. The patient had a history of type 1 diabetes mellitus (DM) with recurrent episodes of ketoacidosis and systemic diabetic complications, including severe gastroparesis. CT scan studies demonstrated EG with venous air, and endoscopy showed severe gastritis and ulcerations. In the gastric biopsies, abundant Sarcina ventriculi were noted in areas of mucosal/submucosal necrosis. Antibiotic treatment was instituted at admission, and subsequent endoscopy demonstrated the disappearance of Sarcina, with some improvement of the gastric inflammation; however, the patient developed septic shock with multiorgan failure and expired. This case highlights the need to consider other infectious etiologies in transplant patients, in addition to the well-known opportunistic infections.

Prognostic value of tumor infiltrating lymphocytes in epithelioid malignant pleural mesothelioma

e20064

Background: Malignant Mesothelioma (MM) is an aggressive malignancy with survival of 4-12 mo. without treatment and 10% 5-year survival. The response of patients with MM to immunotherapy has increased interest in the tumor immune microenvironment. The purpose of this study was to determine if tumor infiltrating lymphocytes (TIL) are correlated with survival in epithelioid MM. Methods: Immunohistochemistry was performed on specimens from 27 patients with epithelioid mesothelioma using CD4, CD8, and CD68 antibodies. Infiltrate density was scored (0-3+) by pathologist estimate in intratumoral and adjacent tumoral tissue. ANOVA and regression analysis were performed. Overall survival (OS) for the entire group and time to progression (TTP) for nine patients with known time from surgery until tumor recurrence were also studied as a surgical resection subgroup (SRG). Results: For the small SRG the relationship between (TTP) and TIL score of CD8 at the edge of the tumor was significant (F[2,6]=5.64, P=.042) however TIL score of intratumoral CD8 cell infiltrates and TTP did not demonstrate statistical significance. The relationship between OS with CD8 infiltrate at the tumor edge, for the entire group, approached significance at (F [3,22]=2.93, P=0.056). TTP and OS and the TIL score of CD4, CD68 at both tumor center and tumor edge did not demonstrate statistical significance. Conclusions: CD8+ lymphocytes are an important component of host immune defense against cancer. We found that in epithelioid MM the cellular infiltrate of CD8 lymphocytes at the edge of the tumor (but not with intratumoral CD8) was associated with longer time to recurrence. TTP and OS were not associated with CD4 and CD68 within or at the tumor edge. The role of CD8 T-cells and the quantitative difference between CD8 at the edge of tumor and intratumoral CD8 should be further investigated in order to optimize immunotherapy.