Abstract 6649: Inhibiting adenosine signaling and KRAS enhances the effect of α-PD-1 therapy in a KRASG12C/TP53R172H/+ pancreatic cancer model

Introduction: High levels of adenosine (ADO) in the tumor microenvironment have been shown to suppress immune responses and curtail T cell activation in the presence of anti-PD-1/PD-L1 blocking antibodies. CD73 catalyzes the extracellular generation of ADO from adenosine monophosphate (AMP). KRAS mutations, of which 60% were derived from pancreatic ductal adenocarcinoma (PDAC) samples, were associated with significantly upregulated CD73 expression, which resulted in a worsening prognosis. These immunosuppressive effects can be counteracted by CD73 inhibitors or by a dual ADO receptor (A2aR/A2bR) antagonist.

Method: Linear models were used to evaluate the ability of 299 pan-cancer consensus oncogenic drivers to predict CD73 expression independent of tumor type in the TCGA dataset. Changes in gene expression induced by KRAS inhibition were determined by RNAseq. Metabolic and proteomic alterations induced by KRAS inhibition were determined by LC-MS. C57BL/6J mice bearing established KP4662-G12C (KRASG12C/TP53R172H/+) tumors (at least 150 mm3) were treated as indicated: A1421 (CD73i; 30 mg/kg/day, s.c.), anti-PD1 (Clone RMP 1-14; 10 mg/kg; twice per week, i.p), and MRTX-1257 (KRASi, 100 mg/kg/day, p.o.). Treatment efficacy was monitored in a blinded manner using micro-computed tomography (mCT). A1412 and MRTX-1257 were provided by Arcus Biosciences.

Data: Direct KRAS inhibition reduced but did not abolish CD73 and A2aR/A2bR expression in multiple PDAC models. Metabolic analyses indicated that KRAS inhibition increased ADO and AMP levels. KRAS inhibition in PDAC models induced gene expression changes consistent with increased tumor immunogenicity. In a murine model of pancreatic cancer-bearing the KRASG12C mutation, co-administration of a CD73 inhibitor with anti-PD-1 in established tumors resulted in significant tumor growth retardation, comparable to KRASG12C inhibition alone. Durable tumor regression was observed when mice were treated with the triple combination therapy. These data support the rationale for the clinical development of modulators of immunosuppressive adenosine signaling in pancreatic cancer.

Conclusion: Here, we show that direct inhibition of mutant KRAS in pancreatic cancer models yields complex immunomodulatory effects. While antigen presentation pathways are transcriptionally upregulated and the expression of immunosuppressive chemokine is reduced, KRAS inhibition also reprograms nucleotide metabolism leading to elevated levels of ADO. These findings suggest that co-targeting mutant KRAS and adenosine signaling may enhance immunotherapy against pancreatic cancer and potentially other KRAS driven malignancies.

Citation Format: THUC LE, Evan Abt, Woosuk Kim, Akshata Udyavar, Arthur Cho, Joe Capri, Jing Cui, Razmik Ghukasyan, Luyi Li, Daniel DiRenzo, Brandon Rosen, Timothy Donahue, Matt Walters, Caius Radu. Inhibiting adenosine signaling and KRAS enhances the effect of α-PD-1 therapy in a KRASG12C/TP53R172H/+ pancreatic cancer model [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 6649.

Phospho-Network Analysis Identifies and Quantifies Hepatitis C Virus (HCV)-induced Hepatocellular Carcinoma (HCC) Proteins Regulating Viral-mediated Tumor Growth

BACKGROUND

Patients with chronic hepatitis C virus (HCV) infection are at risk of serious complications of cirrhosis and hepatocellular carcinoma (HCC). Mass spectrometry (MS) is a versatile methodology that produces a global proteomic landscape for analysis of cancer mechanisms.

MATERIALS AND METHODS

Using multiplex peptide stable isotopic labeling and immobilized metal affinity chromatography (IMAC), we enriched and quantified the phosphoproteome of HCC, with and without HCV. While raw data identified protein targets based on expression alone, we also used abundance groups for comprehensive functional analysis.

RESULTS

Analysis of functional differences highlighted deregulated phosphoprotein networks. This uncovered additional candidates that could be directly derived from the MS data. Cellular processes and pathways that may differ with HCV infection include: cytoskeletal dynamics, insulin response, gene expression, and PI3K/AKT oncogenesis.

CONCLUSION

This function-focused workflow provides a simple framework to analyze MS data. Phosphoproteome quantitation with inclusive functional analysis can generate hypotheses for liver cancer research to improve early screening and identification of molecular targets for therapy.

The Structure and Interactions of Periplasmic Domains of Crucial MmpL Membrane Proteins from Mycobacterium tuberculosis

Mycobacterium tuberculosis mycobacterial membrane protein large (MmpL) proteins are important in substrate transport across the inner membrane. Here, we show that MmpL proteins are classified into two phylogenetic clusters, where MmpL cluster II contains three soluble domains (D1, D2, and D3) and has two full-length members, MmpL3 and MmpL11. Significantly, MmpL3 is currently the most druggable M. tuberculosis target. We have solved the 2.4-Å MmpL11-D2 crystal structure, revealing structural homology to periplasmic porter subdomains of RND (multidrug) transporters. The resulting predicted cluster II MmpL membrane topology has D1 and D2 residing, and possibly interacting, within the periplasm. Crosslinking and biolayer interferometry experiments confirm that cluster II D1 and D2 bind with weak affinities, and guided D1-D2 heterodimeric model assemblies. The predicted full-length MmpL3 and MmpL11 structural models reveal key substrate binding and transport residues, and may serve as templates to set the stage for in silico anti-tuberculosis drug development.

Septin dynamics are essential for exocytosis

Septins are a family of 14 cytoskeletal proteins that dynamically form hetero-oligomers and organize membrane microdomains for protein complexes. The previously reported interactions with SNARE proteins suggested the involvement of septins in exocytosis. However, the contradictory results of up- or down-regulation of septin-5 in various cells and mouse models or septin-4 in mice suggested either an inhibitory or a stimulatory role for these septins in exocytosis. The involvement of the ubiquitously expressed septin-2 or general septin polymerization in exocytosis has not been explored to date. Here, by nano-LC with tandem MS and immunoblot analyses of the septin-2 interactome in mouse brain, we identified not only SNARE proteins but also Munc-18-1 (stabilizes assembled SNARE complexes), N-ethylmaleimide-sensitive factor (NSF) (disassembles SNARE complexes after each membrane fusion event), and the chaperones Hsc70 and synucleins (maintain functional conformation of SNARE proteins after complex disassembly). Importantly, α-soluble NSF attachment protein (SNAP), the adaptor protein that mediates NSF binding to the SNARE complex, did not interact with septin-2, indicating that septins undergo reorganization during each exocytosis cycle. Partial depletion of septin-2 by siRNA or impairment of septin dynamics by forchlorfenuron inhibited constitutive and stimulated exocytosis of secreted and transmembrane proteins in various cell types. Forchlorfenuron impaired the interaction between SNAP-25 and its chaperone Hsc70, decreasing SNAP-25 levels in cultured neuroendocrine cells, and inhibited both spontaneous and stimulated acetylcholine secretion in mouse motor neurons. The results demonstrate a stimulatory role of septin-2 and the dynamic reorganization of septin oligomers in exocytosis.

Drip, Ship, and Grip, then Slice and Dice: Comprehensive Stroke Center Management of Cervical and Intracranial Emboli

BACKGROUND AND PURPOSE

Tandem acute thrombotic emboli in the cervical and intracranial arteries are an unusual cause of stroke presenting unique management challenges. In regional systems of acute stroke care anchored by Comprehensive Stroke Centers (CSC), combined fibrinolytic, endovascular, and open surgical intervention is a new therapeutic option.

SUMMARY OF CASE

A 28-year-old male underwent retinal surgery, including post-operative neck compression and the next day presented to a primary stroke center with aphasia and right hemiplegia. Intravenous tissue plasminogen activator therapy was initiated and the patient was transferred to a CSC for higher level of care (drip and ship). Imaging at the CSC demonstrated tandem thrombi: a near occlusive lesion at the origin of the left cervical internal carotid artery and a total occlusion of the M1 segment of the left middle cerebral artery. Endovascular thrombectomy with the Solitaire stent retriever resulted in intracranial recanalization (grip). Immediately after the endovascular procedure, open carotid thrombectomy was performed to achieve cervical carotid revascularization without systemic heparinization (slice). Both cervical carotid and intracranial thrombi were processed for proteomic analysis via mass spectrometry (dice).

CONCLUSION

Combined fibrinolytic, endovascular, and open surgical intervention can yield revascularization and good clinical outcome in cases of tandem lesions.