Lequn Li

During activation, T cells undergo metabolic reprogramming, which imprints distinct functional fates. We determined that on PD-1 ligation, activated T cells are unable to engage in glycolysis or amino acid metabolism but have an increased rate of fatty acid β-oxidation (FAO). PD-1 promotes FAO of endogenous lipids by increasing expression of CPT1A, and inducing lipolysis as indicated by elevation of the lipase ATGL, the lipolysis marker glycerol and release of fatty acids. Conversely, CTLA-4 inhibits glycolysis without augmenting FAO, suggesting that CTLA-4 sustains the metabolic profile of non-activated cells. Because T cells utilize glycolysis during differentiation to effectors, our findings reveal a metabolic mechanism responsible for PD-1-mediated blockade of T-effector cell differentiation. The enhancement of FAO provides a mechanistic explanation for the longevity of T cells receiving PD-1 signals in patients with chronic infections and cancer, and for their capacity to be reinvigorated by PD-1 blockade.

Rational: LDCT screening can identify early-stage lung cancers yet introduces excessive false positives and it remains a great challenge to differentiate malignant tumors from benign solitary pulmonary nodules, which calls for better non-invasive diagnostic tools. Methods: We performed DNA methylation profiling by high throughput DNA bisulfite sequencing in tissue samples (nodule size < 3 cm in diameter) to learn methylation patterns that differentiate cancerous tumors from benign lesions. Then we filtered out methylation patterns exhibiting high background in circulating tumor DNA (ctDNA) and built an assay for plasma sample classification. Results: We first performed methylation profiling of 230 tissue samples to learn cancer-specific methylation patterns which achieved a sensitivity of 92.7% (88.3% -97.1%) and a specificity of 92.8% (89.3% -96.3%). These tissue-derived DNA methylation markers were further filtered using a training set of 66 plasma samples and 9 markers were selected to build a diagnostic prediction model. From an independent validation set of additional 66 plasma samples, this model obtained a sensitivity of 79.5% (63.5% -90.7%) and a specificity of 85.2% (66.3% -95.8%) for differentiating patients with malignant tumor (n = 39) from patients with benign lesions (n = 27). Additionally, when tested on gender and age matched asymptomatic normal individuals (n = 118), our model achieved a specificity of 93.2% (89.0% -98.3%). Specifically, our assay is highly sensitive towards early-stage lung cancer, with a sensitivity of 75.0% (55.0%-90.0%) in 20 stage Ia lung cancer patients and 85.7% (57.1%-100.0%) in 7 stage Ib lung cancer patients.

IFN‐γ plays a crucial role in anti‐tumor responses and also induces expression of PD‐L1, a well‐established inhibitor of anti‐tumor immune function. Understanding how molecular signaling regulates the function of IFN‐γ might improve its anti‐tumor efficacy. Here, we show that the tumor expression of IFN‐γ expression alone has no significant prognostic value in patients with locally advanced lung adenocarcinoma. Surprisingly, patients with tumors expressing both IFN‐γ and PD‐L1 have the best prognosis compared to those with tumors expressing IFN‐γ or PD‐L1 alone. Transcriptome analysis demonstrated that tumor tissues expressing IFN‐γ display gene expression associated with suppressed cell cycle progression and expansion. Unexpectedly this profile was observed in PD‐L1 + but not PD‐L1− tumors. The current concept is that PD‐L1 functions as a shield protecting tumor cells from cytolytic T cell (CTL)‐mediated anti‐tumor progression. However, our data indicate that PD‐L1 expression in the presence of IFN‐γ might serve as biomarker for the sensitivity of tumors to the inhibitory effect of IFN‐γ. Mechanistic analysis revealed that in lung adenocarcinoma cells IFN‐γ‐induced activation of JAK2‐STAT1 and PI3K‐AKT pathways. The activation of JAK2‐STAT1 is responsible for the anti‐proliferative effect of IFN‐γ. Inhibition of PI3K downregulated PD‐L1 expression and enhanced the anti‐proliferative effect of IFN‐γ, suggesting that blockade of PI3K might maximize the IFN‐γ‐mediated anti‐tumor effect. Our findings provide evidence for crosstalk between JAK2‐STAT1 and PI3K‐AKT pathways in response to IFN‐γ in lung adenocarcinoma and have implications for the design of combinatorial targeted therapy and immunotherapy for the treatment of lung adenocarcinoma.