Edwin J. Ostrin

Immunoproteasome deficiency is a feature of non-small cell lung cancer with a mesenchymal phenotype and is associated with a poor outcome

Significance The success rate of therapeutic trials that target tumor antigens is quite limited. We demonstrate for the first time to our knowledge that lung cancer cells that have undergone epithelial-to-mesenchymal transition lose immunoproteasome expression, resulting in markedly reduced antigen presentation. Reduced expression of the immunoproteasome was associated with and can predict poor outcome in non-small cell lung carcinoma (NSCLC) patients. Induction of the immunoproteasome with IFNγ or 5-aza-2′-deoxycytidine (5-aza-dC) treatment can overcome this immune escape mechanism of mesenchymal cells by restoring functional HLA class I-bound peptides. These findings have substantial relevance for development of effective strategies to target tumor cells with inherent resistance to T cell-mediated immunotherapy. The immunoproteasome plays a key role in generation of HLA peptides for T cell-mediated immunity. Integrative genomic and proteomic analysis of non-small cell lung carcinoma (NSCLC) cell lines revealed significantly reduced expression of immunoproteasome components and their regulators associated with epithelial to mesenchymal transition. Low expression of immunoproteasome subunits in early stage NSCLC patients was associated with recurrence and metastasis. Depleted repertoire of HLA class I-bound peptides in mesenchymal cells deficient in immunoproteasome components was restored with either IFNγ or 5-aza-2′-deoxycytidine (5-aza-dC) treatment. Our findings point to a mechanism of immune evasion of cells with a mesenchymal phenotype and suggest a strategy to overcome immune evasion through induction of the immunoproteasome to increase the cellular repertoire of HLA class I-bound peptides.

IL6 Blockade Reprograms the Lung Tumor Microenvironment to Limit the Development and Progression of K-ras–Mutant Lung Cancer

Activating mutations of K-ras are the most common oncogenic alterations found in lung cancer. Unfortunately, attempts to target K-ras-mutant lung tumors have thus far failed, clearly indicating the need for new approaches in patients with this molecular profile. We have previously shown NF-κB activation, release of IL6, and activation of its responsive transcription factor STAT3 in K-ras-mutant lung tumors, which was further amplified by the tumor-enhancing effect of chronic obstructive pulmonary disease (COPD)-type airway inflammation. These findings suggest an essential role for this inflammatory pathway in K-ras-mutant lung tumorigenesis and its enhancement by COPD. Therefore, here we blocked IL6 using a monoclonal anti-IL6 antibody in a K-ras-mutant mouse model of lung cancer in the absence or presence of COPD-type airway inflammation. IL6 blockade significantly inhibited lung cancer promotion, tumor cell-intrinsic STAT3 activation, tumor cell proliferation, and angiogenesis markers. Moreover, IL6 inhibition reduced expression of protumor type 2 molecules (arginase 1, Fizz 1, Mgl, and IDO), number of M2-type macrophages and granulocytic myeloid-derived suppressor cells, and protumor T-regulatory/Th17 cell responses. This was accompanied by increased expression of antitumor type 1 molecule (Nos2), and antitumor Th1/CD8 T-cell responses. Our study demonstrates that IL6 blockade not only has direct intrinsic inhibitory effect on tumor cells, but also reeducates the lung microenvironment toward an antitumor phenotype by altering the relative proportion between protumor and antitumor immune cells. This information introduces IL6 as a potential druggable target for prevention and treatment of K-ras-mutant lung tumors. Cancer Res; 76(11); 3189-99. ©2016 AACR.

The development and plasticity of alveolar type 1 cells

Alveolar type 1 (AT1) cells cover >95% of the gas exchange surface and are extremely thin to facilitate passive gas diffusion. The development of these highly specialized cells and its coordination with the formation of the honeycomb-like alveolar structure are poorly understood. Using new marker-based stereology and single-cell imaging methods, we show that AT1 cells in the mouse lung form expansive thin cellular extensions via a non-proliferative two-step process while retaining cellular plasticity. In the flattening step, AT1 cells undergo molecular specification and remodel cell junctions while remaining connected to their epithelial neighbors. In the folding step, AT1 cells increase in size by more than 10-fold and undergo cellular morphogenesis that matches capillary and secondary septa formation, resulting in a single AT1 cell spanning multiple alveoli. Furthermore, AT1 cells are an unexpected source of VEGFA and their normal development is required for alveolar angiogenesis. Notably, a majority of AT1 cells proliferate upon ectopic SOX2 expression and undergo stage-dependent cell fate reprogramming. These results provide evidence that AT1 cells have both structural and signaling roles in alveolar maturation and can exit their terminally differentiated non-proliferative state. Our findings suggest that AT1 cells might be a new target in the pathogenesis and treatment of lung diseases associated with premature birth. Highlighted article: Mouse lung alveolar type 1 cells form expansive thin cellular extensions via a non-proliferative two-step process, while retaining cellular plasticity.

The Emerging Role of B Cells in Tumor Immunity

There is increasing evidence supporting a role for B cells in tumor immunology. Paraneoplastic syndromes occurring before a cancer diagnosis have pointed to the potential for harnessing the humoral immune response for early cancer detection. The presence of tumor-infiltrating B lymphocytes has been linked to a favorable clinical outcome in many types of cancers. However, B cells represent a heterogeneous population with functionally distinct subsets, and the balance among subtypes impacts tumor development. Here, we review recent findings related to B cells and to the humoral immune response in cancer and their translational significance. Cancer Res; 76(19); 5597-601. ©2016 AACR.

MCAM mediates chemoresistance in small-cell lung cancer via the PI3K/AKT/ SOX2 signaling pathway

Despite favorable responses to initial therapy, small-cell lung cancer (SCLC) relapse occurs within a year and exhibits resistance to multiple drugs. Because of limited accessibility of patient tissues for research purposes, SCLC patient-derived xenografts (PDX) have provided the best opportunity to address this limitation. Here, we sought to identify novel mechanisms involved in SCLC chemoresistance. Through in-depth proteomic profiling, we identified MCAM as a markedly upregulated surface receptor in chemoresistant SCLC cell lines and in chemoresistant PDX compared with matched treatment-naïve tumors. MCAM depletion in chemoresistant cells reduced cell proliferation and reduced the IC50 inhibitory concentration of chemotherapeutic drugs in vitro This MCAM-mediated sensitization to chemotherapy occurred via SOX2-dependent upregulation of mitochondrial 37S ribosomal protein 1/ATP-binding cassette subfamily C member 1 (MRP1/ABCC1) and the PI3/AKT pathway. Metabolomic profiling revealed that MCAM modulated lactate production in chemoresistant cells that exhibit a distinct metabolic phenotype characterized by low oxidative phosphorylation. Our results suggest that MCAM may serve as a novel therapeutic target to overcome chemoresistance in SCLC. Cancer Res; 77(16); 4414-25. ©2017 AACR.

Plasma-derived extracellular vesicle proteins as a source of biomarkers for lung adenocarcinoma

Exosomes and other extracellular vesicles (EVs) have been implicated as mediators of intercellular communication. Their release into the circulation has the potential to inform about tumor status. In-depth proteomic characterization of plasma-derived EVs has been limited by challenges in isolating EVs from protein-abundant biological fluids. We implemented a novel single-step density gradient flotation workflow for efficient and rapid isolation of highly enriched circulating EVs from plasma. Mass-spectrometry analysis of plasma EVs from subjects with lung adenocarcinoma and matched controls resulted in the identification of 640 proteins. A total of 108 proteins exhibited significant (p<0.05) differential expression in vesicle preparations derived from lung adenocarcinoma case plasmas compared to controls, of which 43 were also identified in EVs from lung adenocarcinoma cell lines. Four top performing EV-associated proteins that distinguished adenocarcinoma cases from controls, SRGN, TPM3, THBS1 and HUWE1, yielded a combined area under the receiver operating characteristic curve (AUC) of 0.90 (95% CI = 0.76-1). Our findings support the potential of EV derived proteins as a source of biomarkers that complement other approaches for tumor assessment.

Role of CPS1 in cell growth, metabolism, and prognosis in LKB1-inactivated lung adenocarcinoma

Background Liver kinase B1 ( LKB1 ) is a tumor suppressor in lung adenocarcinoma (LADC). We investigated the proteomic profiles of 45 LADC cell lines with and without LKB1 inactivation. Carbamoyl phosphate synthetase 1 (CPS1), the first rate-limiting mitochondrial enzyme in the urea cycle, was distinctively overexpressed in LKB1-inactivated LADC cell lines. We therefore assessed the role of CPS1 and its clinical relevance in LKB1-inactivated LADC. Methods Mass spectrometric profiling of proteome and metabolome and function of CPS1 were analyzed in LADC cell lines. CPS1 and LKB1 expression in tumors from 305 LADC and 160 lung squamous cell carcinoma patients was evaluated by immunohistochemistry. Kaplan-Meier and Cox regression analyses were applied to assess the association between overall survival and CPS1 and LKB1 expression. All statistical tests were two-sided. Results CPS1 knockdown reduced cell growth, decreased metabolite levels associated with nucleic acid biosynthesis pathway, and contributed an additive effect when combined with gemcitabine, pemetrexed, or CHK1 inhibitor AZD7762. Tissue microarray analysis revealed that CPS1 was expressed in 65.7% of LKB1-negative LADC, and only 5.0% of LKB1-positive LADC. CPS1 expression showed statistically significant association with poor overall survival in LADC (hazard ratio = 3.03, 95% confidence interval = 1.74 to 5.25, P < .001). Conclusions Our findings suggest functional relevance of CPS1 in LKB1-inactivated LADC and association with worse outcome of LADC. CPS1 is a promising therapeutic target in combination with other chemotherapy agents, as well as a prognostic biomarker, enabling a personalized approach to treatment of LADC.BACKGROUND Liver kinase B1 (LKB1) is a tumor suppressor in lung adenocarcinoma (LADC). We investigated the proteomic profiles of 45 LADC cell lines with and without LKB1 inactivation. Carbamoyl phosphate synthetase 1 (CPS1), the first rate-limiting mitochondrial enzyme in the urea cycle, was distinctively overexpressed in LKB1-inactivated LADC cell lines. We therefore assessed the role of CPS1 and its clinical relevance in LKB1-inactivated LADC. METHODS Mass spectrometric profiling of proteome and metabolome and function of CPS1 were analyzed in LADC cell lines. CPS1 and LKB1 expression in tumors from 305 LADC and 160 lung squamous cell carcinoma patients was evaluated by immunohistochemistry. Kaplan-Meier and Cox regression analyses were applied to assess the association between overall survival and CPS1 and LKB1 expression. All statistical tests were two-sided. RESULTS CPS1 knockdown reduced cell growth, decreased metabolite levels associated with nucleic acid biosynthesis pathway, and contributed an additive effect when combined with gemcitabine, pemetrexed, or CHK1 inhibitor AZD7762. Tissue microarray analysis revealed that CPS1 was expressed in 65.7% of LKB1-negative LADC, and only 5.0% of LKB1-positive LADC. CPS1 expression showed statistically significant association with poor overall survival in LADC (hazard ratio = 3.03, 95% confidence interval = 1.74 to 5.25, P < .001). CONCLUSIONS Our findings suggest functional relevance of CPS1 in LKB1-inactivated LADC and association with worse outcome of LADC. CPS1 is a promising therapeutic target in combination with other chemotherapy agents, as well as a prognostic biomarker, enabling a personalized approach to treatment of LADC.

β-catenin maintains lung epithelial progenitors after lung specification

ABSTRACT The entire lung epithelium arises from SRY box 9 (SOX9)-expressing progenitors that form the respiratory tree and differentiate into airway and alveolar cells. Despite progress in understanding their initial specification within the embryonic foregut, how these progenitors are subsequently maintained is less clear. Using inducible, progenitor-specific genetic mosaic mouse models, we showed that β-catenin (CTNNB1) maintains lung progenitors by promoting a hierarchical lung progenitor gene signature, suppressing gastrointestinal (GI) genes, and regulating NK2 homeobox 1 (NKX2.1) and SRY box 2 (SOX2) in a developmental stage-dependent manner. At the early, but not later, stage post-lung specification, CTNNB1 cell-autonomously maintained normal NKX2.1 expression levels and suppressed ectopic SOX2 expression. Genetic epistasis analyses revealed that CTNNB1 is required for fibroblast growth factor (Fgf)/Kirsten rat sarcoma viral oncogene homolog (Kras)-mediated promotion of the progenitors. In silico screening of Eurexpress and translating ribosome affinity purification (TRAP)-RNAseq identified a progenitor gene signature, a subset of which depends on CTNNB1. Wnt signaling also maintained NKX2.1 expression and suppressed GI genes in cultured human lung progenitors derived from embryonic stem cells. Summary: CTNNB1-mediated Wnt signaling maintains lung fate and suppresses gastrointestinal fate of mouse and human SOX9 progenitors, maintaining NKX2.1 and inhibiting SOX2 in a developmental stage-specific manner.

Reduced IL-6 levels and tumor-associated phospho-STAT3 are associated with reduced tumor development in a mouse model of lung cancer chemoprevention with myo-inositol

Several promising chemopreventive agents have for lung cancer emerged in preclinical models and in retrospective trials. These agents have been shown to modulate pathways altered in carcinogenesis and reduce markers of carcinogenesis in animal and cell culture models. Cancer‐prone transgenic mice with oncogenic Kras expressed in the airway epithelium (CcspCre/+; KrasLSL‐G12D/+) were raised on diets compounded with myo‐inositol. These animals form lung premalignant lesions in a stereotypical fashion over the ten weeks following weaning. Mice raised on myo‐inositol containing diets showed potent reduction in the number, size, and stage of lesions as compared to those raised on control diets. myo‐inositol has previously been reported to inhibit phosphoinositide 3‐kinase (PI3K) signaling. However, in mice raised on myo‐inositol, total PI3K signaling was largely unaffected. Proteomic and cytokine analyses revealed large reduction in IL‐6 related pathways, including STAT3 phosphorylation. This effect was not due to direct inhibition of IL‐6 production and autocrine signaling within the tumor cell, but rather through alteration in macrophage recruitment and in phenotype switching, with an increase in antitumoral M1 macrophages.

Abstract 2775: CPS1 as a therapeutic target and prognostic indicator in LKB1-inactivated lung adenocarcinoma

Liver Kinase B1 (LKB1), encoded by STK11, is a tumor suppressor and somatically mutated in approximately 20% of lung adenocarcinoma. Aside from the effects of LKB1 inactivation on tumor initiation, LKB1-mutant cancers are biologically distinct from cancer with functional LKB1, and the loss of LKB1 uniquely confers invasive and metastatic properties in genetically engineered mouse models of cancer. While various pathways, including energy metabolism, cell polarity, and cell growth, are regulated by LKB1 and can play a pleiotropic role in cancer initiation and progression, no therapies are currently available for clinical use that specifically target LKB1 inactivation. Therefore, elucidation of the functional mechanisms associated with LKB1 inactivation has translational relevance. We analyzed proteomic profiles of 45 lung adenocarcinoma cell lines with and without LKB1 inactivation to identify molecular features associated with LKB1 inactivation. Carbamoyl phosphate synthase 1 (CPS1) was identified as a markedly overexpressed protein in LKB1-inactivated lung adenocarcinoma cell lines. CPS1 is the first rate-limiting mitochondrial enzyme in the urea cycle, and plays an intricate role in arginine and pyrimidine metabolism. CPS1 knockdown reduced cell growth, decreased levels of metabolites associated with nucleic acid biosynthesis pathway, and contributed an additive effect when combined with conventional chemotherapy agents including gemcitabine, pemetrexed, or CHK1 inhibitor AZD7762. Tissue microarray analysis using 305 lung adenocarcinoma tumors revealed that CPS1 was expressed in 65.7% of LKB1-negative and only 5.0% of LKB1-positive lung adenocarcinomas. In addition, CPS1 expression was significantly and independently associated with poor overall survival of lung adenocarcinoma patients (P Citation Format: Muge Celiktas, Ichidai Tanaka, Satyendra Chandra Tripathi, Johannes F. Fahrmann, Clemente Aguilar-Bonavides, Pamela Villalobos, Oliver Delgado, Dilsher Dhillon, Jennifer B. Dennison, Edwin J. Ostrin, Hong Wang, Carmen Behrens, Kim-Anh Do, Adi F. Gazdar, Samir M. Hanash, Ayumu Taguchi. CPS1 as a therapeutic target and prognostic indicator in LKB1-inactivated lung adenocarcinoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 2775. doi:10.1158/1538-7445.AM2017-2775