Intratumoral plasma cells predict outcomes to PD-L1 blockade in non-small cell lung cancer.

Inhibitors of the programmed cell death-1 (PD-1/PD-L1) signaling axis are approved to treat non-small cell lung cancer (NSCLC) patients, based on their significant overall survival (OS) benefit. Using transcriptomic analysis of 891 NSCLC tumors from patients treated with either the PD-L1 inhibitor atezolizumab or chemotherapy from two large randomized clinical trials, we find a significant B cell association with extended OS with PD-L1 blockade, independent of CD8+ T cell signals. We then derive gene signatures corresponding to the dominant B cell subsets present in NSCLC from single-cell RNA sequencing (RNA-seq) data. Importantly, we find increased plasma cell signatures to be predictive of OS in patients treated with atezolizumab, but not chemotherapy. B and plasma cells are also associated with the presence of tertiary lymphoid structures and organized lymphoid aggregates. Our results suggest an important contribution of B and plasma cells to the efficacy of PD-L1 blockade in NSCLC.

Conformation-locking antibodies for the discovery and characterization of KRAS inhibitors.

Small molecules that stabilize inactive protein conformations are an underutilized strategy for drugging dynamic or otherwise intractable proteins. To facilitate the discovery and characterization of such inhibitors, we created a screening platform to identify conformation-locking antibodies for molecular probes (CLAMPs) that distinguish and induce rare protein conformational states. Applying the approach to KRAS, we discovered CLAMPs that recognize the open conformation of KRASG12C stabilized by covalent inhibitors. One CLAMP enables the visualization of KRASG12C covalent modification in vivo and can be used to investigate response heterogeneity to KRASG12C inhibitors in patient tumors. A second CLAMP enhances the affinity of weak ligands binding to the KRASG12C switch II region (SWII) by stabilizing a specific conformation of KRASG12C, thereby enabling the discovery of such ligands that could serve as leads for the development of drugs in a high-throughput screen. We show that combining the complementary properties of antibodies and small molecules facilitates the study and drugging of dynamic proteins.

CBP/p300 Drives the Differentiation of Regulatory T Cells through Transcriptional and Non-Transcriptional Mechanisms.

Regulatory T cells (Treg) are immunosuppressive and negatively impact response to cancer immunotherapies. CREB-binding protein (CBP) and p300 are closely related acetyltransferases and transcriptional coactivators. Here, we evaluate the mechanisms by which CBP/p300 regulate Treg differentiation and the consequences of CBP/p300 loss-of-function mutations in follicular lymphoma. Transcriptional and epigenetic profiling identified a cascade of transcription factors essential for Treg differentiation. Mass spectrometry analysis showed that CBP/p300 acetylates prostacyclin synthase, which regulates Treg differentiation by altering proinflammatory cytokine secretion by T and B cells. Reduced Treg presence in tissues harboring CBP/p300 loss-of-function mutations was observed in follicular lymphoma. Our findings provide novel insights into the regulation of Treg differentiation by CBP/p300, with potential clinical implications on alteration of the immune landscape. SIGNIFICANCE: This study provides insights into the dynamic role of CBP/p300 in the differentiation of Tregs, with potential clinical implications in the alteration of the immune landscape in follicular lymphoma.

Apolipoprotein E Promotes Invasion in Oral Squamous Cell Carcinoma.

Oral squamous cell carcinoma (OSCC) patients generally have a poor prognosis, because of the invasive nature of these tumors. In comparing transcription profiles between OSCC tumors with a more invasive (worst pattern of tumor invasion 5) versus a less invasive (worst pattern of tumor invasion 3) pattern of invasion, we identified a total of 97 genes that were overexpressed at least 1.5-fold in the more invasive tumor subtype. The most functionally relevant genes were assessed using in vitro invasion assays with an OSCC cell line (UM-SCC-1). Individual siRNA knockdown of 15 of these 45 genes resulted in significant reductions in tumor cell invasion compared to a nontargeting siRNA control. One gene whose knockdown had a strong effect on invasion corresponded to apolipoprotein E (APOE). Both matrix degradation and the number of mature invadopodia were significantly decreased with APOE knockdown. APOE knockdown also resulted in increased cellular cholesterol, consistent with APOE's role in regulating cholesterol efflux. APOE knockdown resulted in decreased levels of phospho-extracellular signal-regulated kinase 1/2, phospho-c-Jun N-terminal kinase, and phospho-cJun, as well as decreased activator protein 1 (AP-1) activity. Expression of matrix metalloproteinase 7 (MMP7), an AP-1 target, was also significantly decreased. Our findings suggest that APOE protein plays a significant role in OSCC tumor invasion because of its effects on cellular cholesterol and subsequent effects on cell signaling and AP-1 activity, leading to changes in the expression of invasion-related proteins, including MMP7.

Mechanisms of Invasion in Head and Neck Cancer.

CONTEXT: The highly invasive properties demonstrated by head and neck squamous cell carcinoma (HNSCC) are often associated with locoregional recurrence and lymph node metastasis in patients and is a key factor leading to an expected 5-year survival rate of approximately 50% for patients with advanced disease. It is important to understand the features and mediators of HNSCC invasion so that new treatment approaches can be developed. OBJECTIVES: To provide an overview of the characteristics, mediators, and mechanisms of HNSCC invasion. DATA SOURCES: A literature review of peer-reviewed articles in PubMed on HNSCC invasion. CONCLUSIONS: Histologic features of HNSCC tumors can help predict prognosis and influence clinical treatment decisions. Cell surface receptors, signaling pathways, proteases, invadopodia function, epithelial-mesenchymal transition, microRNAs, and tumor microenvironment are all involved in the regulation of the invasive behavior of HNSCC cells. Identifying effective HNSCC invasion inhibitors has the potential to improve outcomes for patients by reducing the rate of spread and increasing responsiveness to chemoradiation.