Tumor cell p38 inhibition to overcome immunotherapy resistance

Patients with tumors that do not respond to immune-checkpoint inhibition often harbor a non-T cell-inflamed tumor microenvironment, characterized by the absence of IFN-γ-associated CD8+ T cell and dendritic cell activation. Understanding the molecular mechanisms underlying immune exclusion in non-responding patients may enable the development of novel combination therapies. p38 MAPK is a known regulator of dendritic and myeloid cells however a tumor-intrinsic immunomodulatory role has not been previously described. Here we identify tumor cell p38 signaling as a therapeutic target to potentiate anti-tumor immunity and overcome resistance to immune-checkpoint inhibitors (ICI). Molecular analysis of tumor tissues from patients with human papillomavirus-negative head and neck squamous carcinoma reveals a p38-centered network enriched in non-T cell-inflamed tumors. Pan-cancer single-cell RNA analysis suggests that p38 activation may be an immune-exclusion mechanism across multiple tumor types. P38 knockdown in cancer cell lines increases T cell migration, and p38 inhibition plus ICI in preclinical models shows greater efficacy compared to monotherapies. In a clinical trial of patients refractory to PD1/L1 therapy, pexmetinib, a p38 inhibitor, plus nivolumab demonstrated deep and durable clinical responses. Targeting of p38 with anti-PD1 has the potential to induce the T cell-inflamed phenotype and overcome immunotherapy resistance.

Use of p53 immunohistochemistry in conjunction with routine histology improves risk stratification of patients with Barrett's oesophagus during routine clinical care

AIMS

Abnormal p53 protein expression detected by immunohistochemistry (IHC) in Barrett's oesophagus (BO) is reported to be a prognostic biomarker for progression to high-grade dysplasia (HGD) or oesophageal adenocarcinoma (OAC). We evaluated our use of p53 IHC for patients with BO under surveillance from 2010 to 2016 in a single academic institution.

METHODS AND RESULTS

We identified 78 patients under surveillance for BO who had biopsies evaluated for abnormal p53 expression in conjunction with routine histology and 892 patients who had histological evaluation alone. All available p53 IHC slides were rescored as wild-type or abnormal. We evaluated the risk of subsequent diagnosis with HGD and OAC. p53-tested patients were significantly more likely to be diagnosed with indefinite dysplasia (IND) or low-grade dysplasia (LGD), compared to patients who were not tested (79.5 versus 10.8%, P = 7.4 × 10^-40 ). Almost half (46.9%) of patients with abnormal p53 expression were diagnosed with HGD or OAC within 5 years, compared to 5.9% with wild-type p53, and 7.6% of patients not tested (P = 2.6 × 10^-18 ). However, this difference was heavily influenced by other risk factors, including dysplasia grade, in multivariate analyses. In the subgroup of patients diagnosed with IND (n = 109), abnormal p53 expression was associated with a fourfold increase (1.2-13.3, P = 0.023) in risk of HGD/OAC relative to untested patients diagnosed with IND, independent of other risk factors.

CONCLUSION

In patients under surveillance for BO in a single academic institution, we found evidence that selective use of p53 IHC in conjunction with routine histology modestly improved risk stratification by identifying patients with IND at higher risk of a subsequent diagnosis of HGD or OAC.

Experimental Evolution In Vivo To Identify Selective Pressures during Pneumococcal Colonization

Experimental evolution is a powerful technique to understand how populations evolve from selective pressures imparted by the surrounding environment. With the advancement of whole-population genomic sequencing, it is possible to identify and track multiple contending genotypes associated with adaptations to specific selective pressures. This approach has been used repeatedly with model species in vitro, but only rarely in vivo Herein we report results of replicate experimentally evolved populations of Streptococcus pneumoniae propagated by repeated murine nasal colonization with the aim of identifying gene products under strong selection as well as the population genetic dynamics of infection cycles. Frameshift mutations in one gene, dltB, responsible for incorporation of d-alanine into teichoic acids on the bacterial surface, evolved repeatedly and swept to high frequency. Targeted deletions of dltB produced a fitness advantage during initial nasal colonization coupled with a corresponding fitness disadvantage in the lungs during pulmonary infection. The underlying mechanism behind the fitness trade-off between these two niches was found to be enhanced adherence to respiratory cells balanced by increased sensitivity to host-derived antimicrobial peptides, a finding recapitulated in the murine model. Additional mutations that are predicted to affect trace metal transport, central metabolism, and regulation of biofilm production and competence were also selected. These data indicate that experimental evolution can be applied to murine models of pathogenesis to gain insight into organism-specific tissue tropisms.IMPORTANCE Evolution is a powerful force that can be experimentally harnessed to gain insight into how populations evolve in response to selective pressures. Herein we tested the applicability of experimental evolutionary approaches to gain insight into how the major human pathogen Streptococcus pneumoniae responds to repeated colonization events using a murine model. These studies revealed the population dynamics of repeated colonization events and demonstrated that in vivo experimental evolution resulted in highly reproducible trajectories that reflect the environmental niche encountered during nasal colonization. Mutations impacting the surface charge of the bacteria were repeatedly selected during colonization and provided a fitness benefit in this niche that was counterbalanced by a corresponding fitness defect during lung infection. These data indicate that experimental evolution can be applied to models of pathogenesis to gain insight into organism-specific tissue tropisms.

Low-grade dysplasia diagnosis ratio and progression metrics identify variable Barrett's esophagus risk stratification proficiency in independent pathology practices

BACKGROUND AND AIMS

The diagnosis of low-grade dysplasia (LGD) in Barrett's esophagus (BE) is subject to substantial interobserver variation. Our central aim in this study is to compare independent pathology practices using objective measures of BE risk stratification proficiency, including frequency of diagnosis and rate of progression, with high-grade dysplasia (HGD) or adenocarcinoma (EAC) after the first diagnosis of LGD.

METHODS

We retrospectively evaluated over 29,000 endoscopic biopsy cases to identify 4734 patients under endoscopic biopsy surveillance for BE in a healthcare system with multiple independent pathology practices: a subspecialized GI pathology group (SSGI; 162 BE cases per pathologist annually), 3 high BE volume general surgical pathology practices (GSPs; >50 BE cases per pathologist annually), and multiple low BE volume GSPs (10.6 BE cases per pathologist annually). We measured LGD diagnosis frequencies and rates of diagnostic progression to HGD or EAC in patients diagnosed with LGD.

RESULTS

The proportion of all BE cases diagnosed as LGD (LGD/BE diagnosis ratio) ranged from 1.1% to 6.8% in the different hospital settings (P < .001). The cumulative proportion of patients with HGD or EAC within 2 years of the first diagnosis of LGD was 35.3% in the SSGI and ranged from 1.4% to 14.3% in the GSPs (P < .001). LGD diagnosed by the GSP with the lowest LGD/BE diagnosis ratio had an adjusted risk of progression similar to LGD diagnosed by subspecialists (hazard ratio, .42; 95% CI, .06-3.03). However, when LGD was diagnosed by other generalists, the adjusted risk of progression was 79% to 91% lower than subspecialists (P < .001). When LGD was diagnosed in a low-volume GSP practice, the risk of progression was not significantly increased relative to patients with nondysplastic BE (hazard ratio, 1.3; 95% CI, .4-3.9).

CONCLUSIONS

General surgical pathologists and subspecialists show highly significant differences with respect to LGD/BE ratio, risk of progression relative to nondysplastic BE, crude annual progression rates, and the cumulative 2-year progression rate after LGD. These metrics can be used to assess proficiency in BE risk stratification in historical cases. Some general practitioners were able to achieve results similar to subspecialists. General surgical pathologists with little annual experience evaluating BE biopsy specimens did not successfully risk stratify patients with BE.

Detection of Mutations in Barrett's Esophagus Before Progression to High-Grade Dysplasia or Adenocarcinoma

BACKGROUND & AIMS

Barrett's esophagus (BE) is the greatest risk factor for esophageal adenocarcinoma (EAC), but only a small proportion of patients with BE develop cancer. Biomarkers might be able to identify patients at highest risk of progression. We investigated genomic differences in surveillance biopsies collected from patients whose BE subsequently progressed compared to patients whose disease did not progress.

METHODS

We performed a retrospective case-control study of 24 patients with BE that progressed to high-grade dysplasia (HGD, n = 14) or EAC (n = 10). The control group (n = 73, called non-progressors) comprised patients with BE and at least 5 years of total endoscopic biopsy surveillance without progression to HGD or EAC. From each patient, we selected a single tissue sample obtained more than 1 year before progression (cases) or more than 2 years before the end of follow-up (controls). Pathogenic mutations, gene copy numbers, and ploidy were compared between samples from progressors and non-progressors.

RESULTS

TP53 mutations were detected in 46% of samples from progressors and 5% of non-progressors. In this case-control sample set, TP53 mutations in BE tissues increased the adjusted risk of progression 13.8-fold (95% confidence interval, 3.2-61.0) (P < .001). We did not observe significant differences in ploidy or copy-number profile between groups. We identified 147 pathogenic mutations in 57 distinct genes-the average number of pathogenic mutations was higher in samples from progressors (n = 2.5) than non-progressors (n = 1.2) (P < .001). TP53 and other somatic mutations were recurrently detected in samples with limited copy-number changes (aneuploidy).

CONCLUSIONS

In genomic analyses of BE tissues from patients with or without later progression to HGD or EAC, we found significantly higher numbers of TP53 mutations in BE from patients with subsequent progression. These mutations were frequently detected before the onset of dysplasia or substantial changes in copy number.

Proximal tubule cell response to radiographic contrast media

Renal dysfunction associated with contrast media (CM) administration is generally attributed to reduced renal blood flow. Studies, however, also suggest direct tubular effects of CM, whose mechanisms remain unclear. This study was conducted to assess the chemotoxic effects of iopamidol, a prototypic CM, on a porcine proximal tubule (PT) cell line, LLC-PK(1) cells. Results indicate that iopamidol did not affect cell viability (determined by trypan blue exclusion and fluorescein staining), but did reduce cell proliferation. Moreover, iopamidol altered mitochondrial function, as determined by 3-(4, 5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) reduction and mitochondrial membrane potential. Decreased MTT reduction was evident with all CM tested, and its rapid recovery after CM removal suggests that inhibition of mitochondrial function is reversible. Injury to PT cells by iopamidol is supported by the fact that CM increase extracellular adenosine, an indicator of cellular stress. This study provides greater insight into the mechanism underlying the nephrotoxicity induced by contrast in patients and explains the reversibility of this toxicity.