Racial disparities in follow-up care of early-stage lung cancer survivors

PURPOSE

To investigate if race impacts receipt of follow-up care in lung cancer survivors, we conducted a cross-sectional study in lung cancer survivors recruited through the New Jersey State Cancer Registry (NJSCR).

METHODS

Between May 2019 and December 2019, survivors of early-stage NSCLC were identified and recruited from the NJSCR. Eligible participants were asked to complete a paper survey questionnaire and medical record release form sent to them by mail.

RESULTS

Of the 112 survivors included in the analysis, 78 (70%) were non-Hispanic (NH) Whites and 34 (30%) were NH Blacks. Mean age was 67 years, 61% were female, and 92% had cancer in remission. A total of 82% of participants reported receiving a surveillance scan (CT or PET) within 1 year of completing the study survey. More NH White survivors received a scan within a year compared to NH Black survivors (89% vs 70%; p = 0.02). More NH White survivors (94%) reported that they were informed of the need for follow-up care by their provider compared to NH Blacks (71%; p = 0.002). Only 57% survivors reported receiving a treatment summary. Significant barriers to care were out-of-pocket costs (24%), non-coverage of test (12.5%), and lack of insurance (10%).

CONCLUSIONS

Significant disparity was identified between NH Blacks and NH Whites in receipt of surveillance scans, as well as in receiving information about need for follow-up care. Low income, lack of insurance, and other financial concerns were identified as significant barriers to follow-up care.

IMPLICATIONS FOR CANCER SURVIVORS

Future interventions to increase survivorship care should target specific unmet needs identified in each survivor population.

Prediction of cancer treatment response from histopathology images through imputed transcriptomics

Advances in artificial intelligence have paved the way for leveraging hematoxylin and eosin (H&E)-stained tumor slides for precision oncology. We present ENLIGHT-DeepPT, an approach for predicting response to multiple targeted and immunotherapies from H&E-slides. In difference from existing approaches that aim to predict treatment response directly from the slides, ENLIGHT-DeepPT is an indirect two-step approach consisting of (1) DeepPT, a new deep-learning framework that predicts genome-wide tumor mRNA expression from slides, and (2) ENLIGHT, which predicts response based on the DeepPT inferred expression values. DeepPT successfully predicts transcriptomics in all 16 TCGA cohorts tested and generalizes well to two independent datasets. Our key contribution is showing that ENLIGHT-DeepPT successfully predicts true responders in five independent patients' cohorts involving four different treatments spanning six cancer types with an overall odds ratio of 2.44, increasing the baseline response rate by 43.47% among predicted responders, without the need for any treatment data for training. Furthermore, its prediction accuracy on these datasets is comparable to a supervised approach predicting the response directly from the images, which needs to be trained and tested on the same cohort. ENLIGHT-DeepPT future application could provide clinicians with rapid treatment recommendations to an array of different therapies and importantly, may contribute to advancing precision oncology in developing countries.

SOX9 drives KRAS-induced lung adenocarcinoma progression and suppresses anti-tumor immunity

The SOX9 transcription factor ensures proper tissue development and homeostasis and has been implicated in promoting tumor progression. However, the role of SOX9 as a driver of lung adenocarcinoma (LUAD), or any cancer, remains unclear. Using CRISPR/Cas9 and Cre-LoxP gene knockout approaches in the Kras^G12D-driven mouse LUAD model, we found that loss of Sox9 significantly reduces lung tumor development, burden and progression, contributing to significantly longer overall survival. SOX9 consistently drove organoid growth in vitro, but SOX9-promoted tumor growth was significantly attenuated in immunocompromised mice compared to syngeneic mice. We demonstrate that SOX9 suppresses immune cell infiltration and functionally suppresses tumor associated CD8⁺ T, natural killer and dendritic cells. These data were validated by flow cytometry, gene expression, RT-qPCR, and immunohistochemistry analyses in Kras^G12D-driven murine LUAD, then confirmed by interrogating bulk and single-cell gene expression repertoires and immunohistochemistry in human LUAD. Notably, SOX9 significantly elevates collagen-related gene expression and substantially increases collagen fibers. We propose that SOX9 increases tumor stiffness and inhibits tumor-infiltrating dendritic cells, thereby suppressing CD8⁺ T cell and NK cell infiltration and activity. Thus, SOX9 drives Kras^G12D-driven lung tumor progression and inhibits anti-tumor immunity at least partly by modulating the tumor microenvironment.

Abstract 272: Autophagy and MEK inhibition promotes ferroptosis in liver kinase B1 (Lkb1)-deficient Kras-driven lung tumors

Tumor suppressor Liver Kinase B1 (LKB1) activates 5’-adenosine monophosphate protein kinase (AMPK) and maintains energy homeostasis in response to energy crises. LKB1 and KRAS are the third most frequent co-mutations detected in non-small cell lung cancer (NSCLC), causing aggressive tumor growth and metastases. Unfortunately, standard treatment with RAS-RAF-MEK-ERK signaling pathway inhibitors has minimal therapeutic efficacy in LKB1-mutant KRAS-driven NSCLC. Thus, identifying a novel treatment for patients harboring co-mutations in LKB1 and KRAS is urgently needed. Autophagy degrades and recycles the building blocks for cancer cells to survive metabolic challenges. Using genetically engineered mouse models (GEMMs), we have previously demonstrated that autophagy compensates for Lkb1 loss for Kras-driven lung tumorigenesis; loss of an autophagy-essential gene Atg7 dramatically impaired tumor initiation and tumor growth in KrasG12D/+;Lkb1−/− (KL) lung tumors. This is in sharp contrast to Lkb1 wild-type (WT) (KrasG12D/+;p53−/− (KP)) tumors that are less sensitive to autophagy gene ablation. To further value our discoveries in clinical translational ability, we treated mouse lung tumor derived cell lines (TDCLs) with FDA-approved autophagy inhibitor hydroxychloroquine (HCQ) and MEK inhibitor Trametinib and found that the combination treatment displayed synergistic anti-proliferative effects in KL TDCLs compared to KP TDCLs. To elucidate the underlying mechanism of increased sensitivity of KL TDCLs to Trametinib by autophagy ablation, we performed metabolomic profiling of KL TDCLs with Trametinib, HCQ, or combination treatment and found that several glycolytic and TCA cycle intermediates, amino acids, and ATP levels were significantly upregulated upon treatment with Trametinib, which were significantly reduced by the combination treatment. In addition, the combination treatment significantly reduced mitochondrial membrane potential, basal respiration, and ATP production in KL TDCLs. In vivo studies using tumor allografts, genetically engineered mouse models (GEMMs) and patient-derived xenografts (PDXs) showed anti-tumor activity of the combination treatment on KL tumors, but not in KP tumors. Moreover, we found increased lipid peroxidation indicative of ferroptosis in KL TDCLs and KL PDX tumors with the combination treatment compared to the single agent treatments. Finally, treatment with a ferroptosis inhibitor rescued the reduced KL allograft tumor growth caused by the combination treatment. Taken together, our observations indicate that autophagy upregulation in KL tumors causes resistance to Trametinib treatment by maintaining energy homeostasis for cell survival and inhibits ferroptosis. Therefore, a combination of autophagy and MEK inhibition could be a novel therapeutic strategy to specifically treat LKB1-deficient KRAS-driven NSCLC.

Citation Format: Vrushank Bhatt, Taijin Lan, Wenping Wang, Jerry Kong, Eduardo Cararo Lopes, Khoosheh Khayati, Jianming Wang, Akash Raju, Michael Rangel, Enrique Lopez, Zhixian Sherrie Hu, Xuefei Luo, Xiaoyang Su, Jyoti Malhotra, Wenwei Hu, Sharon R. Pine, Eileen White, Jessie Yanxiang Guo. Autophagy and MEK inhibition promotes ferroptosis in liver kinase B1 (Lkb1)-deficient Kras-driven lung tumors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 272.

Inhibition of autophagy and MEK promotes ferroptosis in Lkb1-deficient Kras-driven lung tumors

LKB1 and KRAS are the third most frequent co-mutations detected in non-small cell lung cancer (NSCLC) and cause aggressive tumor growth. Unfortunately, treatment with RAS-RAF-MEK-ERK pathway inhibitors has minimal therapeutic efficacy in LKB1-mutant KRAS-driven NSCLC. Autophagy, an intracellular nutrient scavenging pathway, compensates for Lkb1 loss to support Kras-driven lung tumor growth. Here we preclinically evaluate the possibility of autophagy inhibition together with MEK inhibition as a treatment for Kras-driven lung tumors. We found that the combination of the autophagy inhibitor hydroxychloroquine (HCQ) and the MEK inhibitor Trametinib displays synergistic anti-proliferative activity in Kras^G12D/+;Lkb1^-/- (KL) lung cancer cells, but not in Kras^G12D/+;p53^-/- (KP) lung cancer cells. In vivo studies using tumor allografts, genetically engineered mouse models (GEMMs) and patient-derived xenografts (PDXs) showed anti-tumor activity of the combination of HCQ and Trametinib on KL but not KP tumors. We further found that the combination treatment significantly reduced mitochondrial membrane potential, basal respiration, and ATP production, while also increasing lipid peroxidation, indicative of ferroptosis, in KL tumor-derived cell lines (TDCLs) and KL tumors compared to treatment with single agents. Moreover, the reduced tumor growth by the combination treatment was rescued by ferroptosis inhibitor. Taken together, we demonstrate that autophagy upregulation in KL tumors causes resistance to Trametinib by inhibiting ferroptosis. Therefore, a combination of autophagy and MEK inhibition could be a novel therapeutic strategy to specifically treat NSCLC bearing co-mutations of LKB1 and KRAS.

Smoking-associated Downregulation of FILIP1L Enhances Lung Adenocarcinoma Progression Through Mucin Production, Inflammation, and Fibrosis

Lung adenocarcinoma (LUAD) is the major subtype in lung cancer, and cigarette smoking is essentially linked to its pathogenesis. We show that downregulation of Filamin A interacting protein 1-like (FILIP1L) is a driver of LUAD progression. Cigarette smoking causes its downregulation by promoter methylation in LUAD. Loss of FILIP1L increases xenograft growth, and, in lung-specific knockout mice, induces lung adenoma formation and mucin secretion. In syngeneic allograft tumors, reduction of FILIP1L and subsequent increase in its binding partner, prefoldin 1 (PFDN1) increases mucin secretion, proliferation, inflammation, and fibrosis. Importantly, from the RNA-sequencing analysis of these tumors, reduction of FILIP1L is associated with upregulated Wnt/β-catenin signaling, which has been implicated in proliferation of cancer cells as well as inflammation and fibrosis within the tumor microenvironment. Overall, these findings suggest that down-regulation of FILIP1L is clinically relevant in LUAD, and warrant further efforts to evaluate pharmacologic regimens that either directly or indirectly restore FILIP1L-mediated gene regulation for the treatment of these neoplasms.

Significance

This study identifies FILIP1L as a tumor suppressor in LUADs and demonstrates that downregulation of FILIP1L is a clinically relevant event in the pathogenesis and clinical course of these neoplasms.

Inhibition of Mtorc1/2 and DNA-PK via CC-115 Synergizes with Carboplatin and Paclitaxel in Lung Squamous Cell Carcinoma

Only a small percentage (<1%) of patients with late-stage lung squamous cell carcinoma (LUSC) are eligible for targeted therapy. Because PI3K/AKT/mTOR signaling, particularly Phosphatidylinositol 3-kinase CA (PIK3CA), is dysregulated in two-thirds of LUSC, and DNA damage response pathways are enriched in LUSC, we tested whether CC-115, a dual mTORC1/2 and DNA-PK inhibitor, sensitizes LUSC to chemotherapy. We demonstrate that CC-115 synergizes with carboplatin in six of 14 NSCLC cell lines, primarily PIK3CA-mutant LUSC. Synergy was more common in cell lines that had decreased basal levels of activated AKT and DNA-PK, evidenced by reduced P-S473-AKT, P-Th308-AKT, and P-S2056-DNA-PKcs. CC-115 sensitized LUSC to carboplatin by inhibiting chemotherapy-induced AKT activation and maintaining apoptosis, particularly in PIK3CA-mutant cells lacking wild-type (WT) TP53. In addition, pathway analysis revealed that enrichments in the IFNα and IFNγ pathways were significantly associated with synergy. In multiple LUSC patient-derived xenograft and cell line tumor models, CC-115 plus platinum-based doublet chemotherapy significantly inhibited tumor growth and increased overall survival as compared with either treatment alone at clinically relevant dosing schedules. IHC and immunoblot analysis of CC-115-treated tumors demonstrated decreased P-Th308-AKT, P-S473-AKT, P-S235/236-S6, and P-S2056-DNA-PKcs, showing direct pharmacodynamic evidence of inhibited PI3K/AKT/mTOR signaling cascades. Because PI3K pathway and DNA-PK inhibitors have shown toxicity in clinical trials, we assessed toxicity by examining weight and numerous organs in PRKDC-WT mice, which demonstrated that the combination treatment does not exacerbate the clinically accepted side effects of standard-of-care chemotherapy. This preclinical study provides strong support for the further investigation of CC-115 plus chemotherapy in LUSC.

Engineered natural killer cells impede the immunometabolic CD73-adenosine axis in solid tumors

Immunometabolic reprogramming due to adenosine produced by CD73 (encoded by the 5’-ectonucleotidase gene NT5E) is a recognized immunosuppressive mechanism contributing to immune evasion in solid tumors. Adenosine is not only known to contribute to tumor progression, but it has specific roles in driving dysfunction of immune cells, including natural killer (NK) cells. Here, we engineered human NK cells to directly target the CD73-adenosine axis by blocking the enzymatic activity of CD73. In doing so, the engineered NK cells not only impaired adenosinergic metabolism driven by the hypoxic uptake of ATP by cancer cells in a model of non-small-cell lung cancer, but also mediated killing of tumor cells due to the specific recognition of overexpressed CD73. This resulted in a ‘single agent’ immunotherapy that combines antibody specificity, blockade of purinergic signaling, and killing of targets mediated by NK cells. We also showed that CD73-targeted NK cells are potent in vivo and result in tumor arrest, while promoting NK cell infiltration into CD73⁺ tumors and enhancing intratumoral activation.

FILIP1L Loss Is a Driver of Aggressive Mucinous Colorectal Adenocarcinoma and Mediates Cytokinesis Defects through PFDN1

Aneuploid mucinous colorectal adenocarcinoma (MAC) is an aggressive subtype of colorectal cancer with poor prognosis. The tumorigenic mechanisms in aneuploid MAC are currently unknown. Here we show that downregulation of Filamin A-interacting protein 1-like (FILIP1L) is a driver of MAC. Loss of FILIP1L increased xenograft growth, and, in colon-specific knockout mice, induced colonic epithelial hyperplasia and mucin secretion. The molecular chaperone prefoldin 1 (PFDN1) was identified as a novel binding partner of FILIP1L at the centrosomes throughout mitosis. FILIP1L was required for proper centrosomal localization of PFDN1 and regulated proteasome-dependent degradation of PFDN1. Importantly, increased PFDN1, caused by downregulation of FILIP1L, drove multinucleation and cytokinesis defects in vitro and in vivo, which were confirmed by time-lapse imaging and 3D cultures of normal epithelial cells. Overall, these findings suggest that downregulation of FILIP1L and subsequent upregulation of PFDN1 is a driver of the unique neoplastic characteristics in aggressive aneuploid MAC. SIGNIFICANCE: This study identifies FILIP1L as a tumor suppressor in mucinous colon cancer and demonstrates that FILIP1L loss results in aberrant stabilization of a centrosome-associated chaperone protein to drive aneuploidy and disease progression.

JAK/STAT of all trades: Linking inflammation with cancer development, tumor progression, and therapy resistance

Inflammation is at the forefront of carcinogenesis, tumor progression, and resistance to therapy. The JAK/STAT signaling axis is a central pathway that mediates the cellular response to inflammation and contributes to carcinogenesis. The JAK/STAT pathway coordinates intercellular communication between tumor cells and their immune microenvironment, and JAK/STAT activation leads to the expression of a variety of proteins involved in cell proliferation, cell survival, stemness, self-renewal, evasion of immunosurveillance mechanisms, and overall tumor progression. Activation of JAK/STAT signaling also mediates resistance to radiation therapy or cytotoxic agents, and modulates tumor cell responses to molecularly targeted and immune modulating drugs. Despite extensive research focused on understanding its signaling mechanisms and downstream phenotypic and functional consequences in hematological disorders, the importance of JAK/STAT signaling in solid tumor initiation and progression has been underappreciated. We highlight the role of chronic inflammation in cancer, the epidemiological evidence for contribution of JAK/STAT to carcinogenesis, the current cancer prevention measures involving JAK/STAT inhibition, and the impact of JAK/STAT signaling activity on cancer development, progression, and treatment resistance. We also discuss recent therapeutic advances in targeting key factors within the JAK/STAT pathway with single agents, and the use of these agents in combination with other targeted therapies and immune checkpoint inhibitors.

Whole-Exome Profiling of NSCLC Among African Americans

INTRODUCTION

Lung cancer incidence is higher among African Americans (AAs) compared with European Americans (EAs) in the United States, especially among men. Although significant progress has been made profiling the genomic makeup of lung cancer in EAs, AAs continue to be underrepresented. Our objective was to chart the genome-wide landscape of somatic mutations in lung cancer tumors from AAs.

METHODS

In this study, we used the whole-exome sequencing of 82 tumor and noninvolved tissue pairs from AAs. Patients were selected from an ongoing case-control study conducted by the National Cancer Institute and the University of Maryland.

RESULTS

Among all samples, we identified 178 significantly mutated genes (p < 0.05), five of which passed the threshold for false discovery rate (p < 0.1). In lung adenocarcinoma (LUAD) tumors, mutation rates in STK11 (p = 0.05) and RB1 (p = 0.008) were significantly higher in AA LUAD tumors (25% and 13%, respectively) compared with The Cancer Genome Atlas EA samples (14% and 4%, respectively). In squamous cell carcinomas, mutation rates in STK11 (p = 0.002) were significantly higher among AA (8%) than EA tumors from The Cancer Genome Atlas (1%). Integrated somatic mutation data with CIBERSORT (Cell-type Identification By Estimating Relative Subsets Of RNA Transcripts) data analysis revealed LUAD tumors from AAs carrying STK11 mutations have decreased interferon signaling.

CONCLUSIONS

Although a considerable degree of the somatic mutation landscape is shared between EAs and AAs, discrete differences in mutation frequency in potentially important oncogenes and tumor suppressors exist. A better understanding of the molecular basis of lung cancer in AA patients and leveraging this information to guide clinical interventions may help reduce disparities.

G protein-coupled kisspeptin receptor induces metabolic reprograming and tumorigenesis in estrogen receptor-negative breast cancer

Triple-negative breast cancer (TNBC) is a highly metastatic and deadly disease. TNBC tumors lack estrogen receptor (ERα), progesterone receptor (PR), and HER2 (ErbB2) and exhibit increased glutamine metabolism, a requirement for tumor growth. The G protein-coupled kisspeptin receptor (KISS1R) is highly expressed in patient TNBC tumors and promotes malignant transformation of breast epithelial cells. This study found that TNBC patients displayed elevated plasma kisspeptin levels compared with healthy subjects. It also provides the first evidence that in addition to promoting tumor growth and metastasis in vivo, KISS1R-induced glutamine dependence of tumors. In addition, tracer-based metabolomics analyses revealed that KISS1R promoted glutaminolysis and nucleotide biosynthesis by increasing c-Myc and glutaminase levels, key regulators of glutamine metabolism. Overall, this study establishes KISS1R as a novel regulator of TNBC metabolism and metastasis, suggesting that targeting KISS1R could have therapeutic potential in the treatment of TNBC.

Strategy to enhance lung cancer treatment by five essential elements: inhalation delivery, nanotechnology, tumor-receptor targeting, chemo- and gene therapy

Non-Small Cell Lung Carcinoma (NSCLC), is the most common type of lung cancer (more than 80% of all cases). Small molecule Tyrosine Kinase (TK) Inhibitors acting on the Epidermal Growth Factor Receptors (EGFRs) are standard therapies for patients with NSCLC harboring EGFR-TK inhibitor-sensitizing mutations. However, fewer than 10 % of patients with NSCLC benefit from this therapy. Moreover, even the latest generation of EGFR inhibitors can cause severe systemic toxicities and are ineffective in preventing non-canonical EGFR signaling. In order to minimize and even overcome these limitations, we are proposing a novel multi-tier biotechnology treatment approach that includes: (1) suppression of all four types of EGFR-TKs by a pool of small interfering RNAs (siRNAs); (2) induction of cell death by an anticancer drug, (3) enhancing the efficiency of the treatment by the local inhalation delivery of therapeutic agents directly to the lungs (passive targeting), (4) active receptor-mediated targeting of the therapy specifically to cancer cells that in turn should minimize adverse side effects of treatment and (5) increasing the stability, solubility, and cellular penetration of siRNA and drug by using tumor targeted Nanostructured Lipid Carriers (NLC). Methods: NLCs targeted to NSCLC cells by a synthetic Luteinizing Hormone-Releasing Hormone (LHRH) decapeptide was used for the simultaneous delivery of paclitaxel (TAX) and a pool of siRNAs targeted to the four major forms of EGFR-TKs. LHRH-NLC-siRNAs-TAX nanoparticles were synthesized, characterized and tested in vitro using human lung cancer cells with different sensitivities to gefitinib (inhibitor of EGFR) and in vivo on an orthotopic NSCLC mouse model. Results: Proposed nanoparticle-based complex containing an anticancer drug, inhibitors of different types of EGFR-TKs and peptide targeted to the tumor-specific receptors (LHRH-NLC-siRNAs-TAX) demonstrated a favorable organ distribution and superior anticancer effect when compared with treatment by a single drug, inhibitor of one EGFR-TK and non-targeted therapy. Conclusions: The use of a multifunctional NLC-based delivery system substantially enhanced the efficiency of therapy for NSCLC and possibly will limit adverse side effects of the treatments. The results obtained have the potential to significantly impact the field of drug delivery and to improve the efficiency of therapy of lung and other types of cancer.

pathCHEMO, a generalizable computational framework uncovers molecular pathways of chemoresistance in lung adenocarcinoma

Despite recent advances in discovering a wide array of novel chemotherapy agents, identification of patients with poor and favorable chemotherapy response prior to treatment administration remains a major challenge in clinical oncology. To tackle this challenge, we present a generalizable genome-wide computational framework pathCHEMO that uncovers interplay between transcriptomic and epigenomic mechanisms altered in biological pathways that govern chemotherapy response in cancer patients. Our approach is tested on patients with lung adenocarcinoma who received adjuvant standard-of-care doublet chemotherapy (i.e., carboplatin-paclitaxel), identifying seven molecular pathway markers of primary treatment response and demonstrating their ability to predict patients at risk of carboplatin-paclitaxel resistance in an independent patient cohort (log-rank p-value = 0.008, HR = 10). Furthermore, we extend our method to additional chemotherapy-regimens and cancer types to demonstrate its accuracy and generalizability. We propose that our model can be utilized to prioritize patients for specific chemotherapy-regimens as a part of treatment planning.

Nusrat Epsi et al. present pathCHEMO, a computational framework for uncovering transcriptomic and epigenomic pathways of chemoresistance in cancer that has the potential to improve clinical decision-making. They apply pathCHEMO to lung adenocarcinoma data from public databases, and identify seven molecular pathways implicated in carboplatin-paclitaxel resistance.

Relationship between West African ancestry with lung cancer risk and survival in African Americans

PURPOSE

African Americans, especially men, have a higher incidence of lung cancer compared with all other racial and ethnic groups in the US. Self-reported race is frequently used in genomic research studies to capture an individual's race or ethnicity. However, it is clear from studies of genetic admixture that human genetic variation does not segregate into the same biologically discrete categories as socially defined categories of race. Previous studies have suggested that the degree of West African ancestry among African Americans can contribute to cancer risk in this population, though few studies have addressed this question in lung cancer.

METHODS

Using a genetic ancestry panel of 100 SNPs, we estimated West African, European, and Native American ancestry in 1,407 self-described African Americans and 2,413 European Americans.

RESULTS

We found that increasing West African ancestry was associated with increased risk of lung cancer among African American men (OR_{Q5 vs Q1} = 2.55 (1.45-4.48), p = 0.001), while no association was observed in African American women (OR_{Q5 vs Q1} = 0.90 (0.51-1.59), p = 0.56). This relationship diminished following adjustment for income and education.

CONCLUSIONS

Genetic ancestry is not a major contributor to lung cancer risk or survival disparities.

Circulating Inflammation Proteins Associated With Lung Cancer in African Americans

INTRODUCTION

Lung cancer incidence is higher among African Americans (AAs) compared with European Americans (EAs) in the United States. We and others have previously shown a relationship between immune and inflammation proteins with lung cancer in EAs. Our aim was to investigate the etiologic relationship between inflammation and lung cancer in AAs.

METHODS

We adopted a two-stage, independent study design (discovery cases, n = 316; control cases, n = 509) (validation cases, n = 399; control cases, n = 400 controls) and measured 30 inflammation proteins in blood using Meso Scale Discovery V- PLEX multiplex assays.

RESULTS

We identified and validated 10 proteins associated with lung cancer in AAS, some that were common between EAs and AAs (C-reactive proteins [OR: 2.90; 95% confidence interval (CI): 1.99-4.22], interferon γ [OR: 1.55; 95% CI: 1.10-2.19], interleukin 6 [OR: 6.28; 95% CI: 4.10-9.63], interleukin 8 [OR: 2.76; 95% CI: 1.92-3.98]) and some that are only observed among AAs (interleukin 10 [OR: 1.69; 95% CI: 1.20-2.38], interleukin 15 [OR: 2.83; 95% CI: 1.96-4.07], interferon gamma-induced protein 10 [OR: 1.54; 95% CI: 1.09-2.18], monocyte chemotactic protein-4 [OR: 0.54; 95% CI: 0.38-0.76], macrophage inflammatory protein-1 alpha [OR: 1.57; 95% CI: 1.12-2.21], and tumor necrosis factor β [OR: 0.52; 95% CI: 0.37-0.74]). We did not find evidence that either menthol cigarette smoking or global genetic ancestry drove these population differences.

CONCLUSIONS

Our results highlight a distinct inflammation profile associated with lung cancer in AAs compared with EAs. These data provide new insight into the etiology of lung cancer in AAs. Further work is needed to understand what drives this relationship with lung cancer and whether these proteins have utility in the setting of early diagnosis.

Rethinking Gamma-secretase Inhibitors for Treatment of Non-small-Cell Lung Cancer: Is Notch the Target?

Lung cancer is the leading cause of cancer-related deaths among men and women. γ-Secretase inhibitors, a class of small-molecule compounds that target the Notch pathway, have been tested to treat non-small-cell lung cancer (NSCLC) in preclinical and clinical trials. Although γ-secretase inhibitors elicit a response in some tumors as single agents and sensitize NSCLC to cytotoxic and targeted therapies, they have not yet been approved for NSCLC therapy. We discuss our recently published preclinical study using the γ-secretase inhibitor AL101, formerly BMS906024, on cell lines and PDX models of NSCLC, primarily lung adenocarcinoma. We propose that Notch pathway mutations may not be the most suitable biomarker for predicting NSCLC response to γ-secretase inhibitors. γ-Secretases have over 100 known γ-secretase cleavage substrates. Many of the γ-secretase substrates are directly involved in carcinogenesis or tumor progression, and are ideal candidates to be the "on-target" biomarkers for γ-secretase inhibitors. We propose the need to systematically test the γ-secretase and other targets as potential biomarkers for sensitivity before continuing clinical trials. Now that we have entered the postgenome/transcriptome era, this goal is easily attainable. Discovery of the biomarker(s) that predict sensitivity to γ-secretase inhibitors would guide selection of the responder population that is most likely to benefit and move the compounds closer to approval for therapeutic use in NSCLC.

Utility of Glioblastoma Patient-Derived Orthotopic Xenografts in Drug Discovery and Personalized Therapy

Despite substantial effort and resources dedicated to drug discovery and development, new anticancer agents often fail in clinical trials. Among many reasons, the lack of reliable predictive preclinical cancer models is a fundamental one. For decades, immortalized cancer cell cultures have been used to lay the groundwork for cancer biology and the quest for therapeutic responses. However, cell lines do not usually recapitulate cancer heterogeneity or reveal therapeutic resistance cues. With the rapidly evolving exploration of cancer “omics,” the scientific community is increasingly investigating whether the employment of short-term patient-derived tumor cell cultures (two- and three-dimensional) and/or patient-derived xenograft models might provide a more representative delineation of the cancer core and its therapeutic response. Patient-derived cancer models allow the integration of genomic with drug sensitivity data on a personalized basis and currently represent the ultimate approach for preclinical drug development and biomarker discovery. The proper use of these patient-derived cancer models might soon influence clinical outcomes and allow the implementation of tailored personalized therapy. When assessing drug efficacy for the treatment of glioblastoma multiforme (GBM), currently, the most reliable models are generated through direct injection of patient-derived cells or more frequently the isolation of glioblastoma cells endowed with stem-like features and orthotopically injecting these cells into the cerebrum of immunodeficient mice. Herein, we present the key strengths, weaknesses, and potential applications of cell- and animal-based models of GBM, highlighting our experience with the glioblastoma stem-like patient cell-derived xenograft model and its utility in drug discovery.

Gamma Secretase Inhibition by BMS-906024 Enhances Efficacy of Paclitaxel in Lung Adenocarcinoma

Notch signaling is aberrantly activated in approximately one third of non-small cell lung cancers (NSCLC). We characterized the interaction between BMS-906024, a clinically relevant Notch gamma secretase inhibitor, and front-line chemotherapy in preclinical models of NSCLC. Chemosensitivity assays were performed on 14 human NSCLC cell lines. There was significantly greater synergy between BMS-906024 and paclitaxel than BMS-906024 and cisplatin [mean combination index (CI) value, 0.54 and 0.85, respectively, P = 0.01]. On an extended panel of 31 NSCLC cell lines, 25 of which were adenocarcinoma, the synergy between BMS-906024 and paclitaxel was significantly greater in KRAS- and BRAF-wildtype than KRAS- or BRAF-mutant cells (mean CI, 0.43 vs. 0.90, respectively; P = 0.003). Paclitaxel-induced Notch1 activation was associated with synergy between BMS-906024 and paclitaxel in the KRAS- or BRAF-mutant group. Knockdown of mutant KRAS increased the synergy between BMS-906024 and paclitaxel in heterozygous KRAS-mutant cell lines. Among KRAS- or BRAF-mutant NSCLC, there was a significant correlation between synergy and mutant or null TP53 status, as well as between synergy and a low H₂O₂ pathway signature. Exogenous overexpression of activated Notch1 or Notch3 had no effect on the enhanced sensitivity of NSCLC to paclitaxel by BMS-906024. In vivo studies with cell line- and patient-derived lung adenocarcinoma xenografts confirmed enhanced antitumor activity for BMS-906024 plus paclitaxel versus either drug alone via decreased cell proliferation and increased apoptosis. These results show that BMS-906024 sensitizes NSCLC to paclitaxel and that wild-type KRAS and BRAF status may predict better patient response to the combination therapy. Mol Cancer Ther; 16(12); 2759-69. ©2017 AACR.

Patient-Derived Xenograft Models of Non-Small Cell Lung Cancer and Their Potential Utility in Personalized Medicine

Traditional preclinical studies of cancer therapeutics have relied on the use of established human cell lines that have been adapted to grow in the laboratory and, therefore, may deviate from the cancer they were meant to represent. With the emphasis of cancer drug development shifting from non-specific cytotoxic agents to rationally designed molecularly targeted therapies or immunotherapy comes the need for better models with predictive value regarding therapeutic activity and response in clinical trials. Recently, the diversity and accessibility of immunodeficient mouse strains has greatly enhanced the production and utility of patient-derived xenograft (PDX) models for many tumor types, including non-small cell lung cancer (NSCLC). Combined with next-generation sequencing, NSCLC PDX mouse models offer an exciting tool for drug development and for studying targeted therapies while utilizing patient samples with the hope of eventually aiding in clinical decision-making. Here, we describe NSCLC PDX mouse models generated by us and others, their ability to reflect the parental tumors’ histomorphological characteristics, as well as the effect of clonal selection and evolution on maintaining genomic integrity in low-passage PDXs compared to the donor tissue. We also raise vital questions regarding the practical utility of PDX and humanized PDX models in predicting patient response to therapy and make recommendations for addressing those questions. Once collaborations and standardized xenotransplantation and data management methods are established, NSCLC PDX mouse models have the potential to be universal and invaluable as a preclinical tool that guides clinical trials and standard therapeutic decisions.

SOX9 is targeted for proteasomal degradation by the E3 ligase FBW7 in response to DNA damage

SOX9 encodes a transcription factor that governs cell fate specification throughout development and tissue homeostasis. Elevated SOX9 is implicated in the genesis and progression of human tumors by increasing cell proliferation and epithelial-mesenchymal transition. We found that in response to UV irradiation or genotoxic chemotherapeutics, SOX9 is actively degraded in various cancer types and in normal epithelial cells, through a pathway independent of p53, ATM, ATR and DNA-PK. SOX9 is phosphorylated by GSK3β, facilitating the binding of SOX9 to the F-box protein FBW7α, an E3 ligase that functions in the DNA damage response pathway. The binding of FBW7α to the SOX9 K2 domain at T236-T240 targets SOX9 for subsequent ubiquitination and proteasomal destruction. Exogenous overexpression of SOX9 after genotoxic stress increases cell survival. Our findings reveal a novel regulatory mechanism for SOX9 stability and uncover a unique function of SOX9 in the cellular response to DNA damage. This new mechanism underlying a FBW7-SOX9 axis in cancer could have implications in therapy resistance.

Abstract 4544: FBW7 induces S-phase arrest caused by DNA double strand breaks through targeting SOX9 for proteasomal degradation

SOX9 encodes a transcription factor that governs cell fate specification throughout development and tissue homeostasis. Elevated SOX9 is implicated in the genesis or progression of many human tumors through increasing cell proliferation and epithelial-mesenchymal transition. We observed that, in response to UV irradiation or certain chemotherapeutic agents, SOX9 is actively and rapidly degraded by a ubiquitin pathway dependent mechanism across several different tumor types including lung cancer, colon cancer, osteosarcoma and melanoma, as well as normal human bronchial epithelial cells. We found that SOX9 is phosphorylated by GSK3β at Ser-236, facilitating the direct binding and degradation of SOX9 via the F box protein, FBW7α. We also determined that the de-ubiquitinase, USP28, stabilizes SOX9 under normal conditions by sequestering FBW7, but is released from FBW7 after UV irradiation, allowing FBW7 to bind SOX9 and target it for destruction. DNA damage-induced SOX9 degradation was independent of p53, ATM, ATR and MAPK pathways. Failure to deplete SOX9 attenuated the DNA damage-induced intra-S-phase checkpoint and increased long-term cell survival. Moreover, mutations within the FBW7 phosphodegron binding site of SOX9 prevented SOX9 degradation after DNA damage, and incurred resistance of non-small cell lung cancer (NSCLC) cells to cisplatin in vivo. We found that cancer patients with tumors expressing high Sox9 and low Fbw7 levels exhibit inferior survival. Our discovery reveals a novel function of SOX9 in the cellular response to DNA damage. Induced degradation of SOX9 may be part of the protection mechanisms to maintain genomic stability. This new regulatory mechanism of the FBW7-SOX9 axis in cancer could have diagnostic and therapeutic implications.

Citation Format: Xuehui Hong, Wenyu Liu, Ruipeng Song, Hiroyuki Inuzuka, Hatem E. Sabaawy, Katherine M. Morgan, Jamie J. Shah, Samuel F. Bunting, Xing Feng, Chi-Kwan Tsang, Zhiyuan Shen, X. F. Steven Zheng, LianXin Liu, Sharon R. Pine. FBW7 induces S-phase arrest caused by DNA double strand breaks through targeting SOX9 for proteasomal degradation. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 4544.

Abstract 4834: Preclinical analysis of the Notch gamma secretase inhibitor BMS-906024 in combination with chemotherapy in the treatment of lung adenocarcinoma

Notch signaling is aberrantly activated in approximately one third of non-small cell lung cancer (NSCLC) cases, primarily through loss of the endogenous Notch inhibitor, Numb, or via gain-of-function mutations in the Notch1 receptor. Notch activity is associated with poor overall survival among NSCLC patients whose tumors are wildtype for TP53. Here, we characterized the interaction between BMS-906024, a clinically relevant gamma secretase inhibitor (GSI) that inhibits Notch activation, and front-line chemotherapy in preclinical models of NSCLC. MTS drug synergy assays consisting of treatment with BMS-906024, cisplatin or paclitaxel, or the combination of GSI and chemotherapy were performed on a panel of human NSCLC cell lines, most of which were derived from adenocarcinomas. Analysis of the drug effects with CalcuSyn yielded significantly lower CI values for the GSI BMS-906024 combined with paclitaxel than with cisplatin (average CI = 0.54 vs 0.85, respectively; P = 0.001). The synergy between BMS-906024 and paclitaxel was significantly greater in Kras-wildtype than Kras-mutant cells (average CI = 0.39 vs 0.68, respectively; P = 0.009), while there was no correlation with EGFR or TP53 status. Treatment of lung adenocarcinoma xenografts in NOD scid gamma mice confirmed enhanced antitumor activity for the combination treatment of BMS-906024 and paclitaxel by mechanisms currently under investigation. These results are a step toward identification of the optimal combination of the GSI BMS-906024 with standard chemotherapies, as well as potential biomarkers that could be used to predict patient response to Notch-targeted therapy.

Citation Format: Katherine M. Morgan, Francis Lee, Erin Michaud, Bruce S. Fischer, Sharon R. Pine. Preclinical analysis of the Notch gamma secretase inhibitor BMS-906024 in combination with chemotherapy in the treatment of lung adenocarcinoma. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 4834.

Differential Serum Cytokine Levels and Risk of Lung Cancer Between African and European Americans

BACKGROUND

African Americans have a higher risk of developing lung cancer than European Americans. Previous studies suggested that certain circulating cytokines were associated with lung cancer. We hypothesized that variations in serum cytokine levels exist between African Americans and European Americans, and increased circulating cytokine levels contribute to lung cancer differently in the two races.

METHODS

Differences in 10 serum cytokine levels, IL1β, IL4, IL5, IL6, IL8, IL10, IL12, granulocyte macrophage colony-stimulating factor, IFNγ, and TNFα, between 170 African-American and 296 European-American controls from the National Cancer Institute-Maryland (NCI-MD) case-control study were assessed. Associations of the serum cytokine levels with lung cancer were analyzed. Statistically significant results were replicated in the prospective Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial and the Wayne State University Karmanos Cancer Institute case-control study.

RESULTS

Six cytokines, IL4, IL5, IL8, IL10, IFNγ, and TNFα, were significantly higher among European-American as compared with African-American controls. Elevated IL6 and IL8 levels were associated with lung cancer among both races in all three studies. Elevated IL1β, IL10, and TNFα levels were associated with lung cancer only among African Americans. The association between elevated TNFα levels and lung cancer among European Americans was significant after adjustment for additional factors.

CONCLUSIONS

Serum cytokine levels vary by race and might contribute to lung cancer differently between African Americans and European Americans.

IMPACT

Future work examining risk prediction models of lung cancer can measure circulating cytokines to accurately characterize risk within racial groups.

Abstract 1957: Negative regulation of Sox9 by glycogen synthase kinase 3 beta phosphorylation and SCFFbw7-dependent ubiquitination in cancer

Sox9 is a member of the SOX [Sry-related high-mobility group (HMG) box] family of transcription factors, with known functions in proliferation, epithelial-mesenchymal transition (EMT), stem cell maintenance and senescence. Sox9 protein levels are elevated in several different cancer types, including lung cancer and osteosarcoma. Furthermore, Sox9 overexpression is associated with poor survival in both cancer types. We recently reported that Sox9 is a direct transcriptional target of the Notch signaling pathway and mediates Notch1-induced EMT in lung cancer (Capaccione et al., Oncotarget, 2014). Fbxw7 (F-box and WD repeat domain-containing 7) is a member of the SCFFbw7E3 ubiquitin ligase complexthat targets several oncogenic proteins for degradation, including Notch1. We hypothesized that Sox9 is targeted for degradation by SCFFbw7. Knocking down or overexpressingFbxw7 significantly increasedor decreased, respectively, endogenous Sox9 protein levels in lung cancer and osteosarcoma cell lines. In addition, overexpression of Fbxw7 resulted in active degradation of ectopic Sox9 protein levels, when assessed in combination with cycloheximide, and did so in a dose dependent-manner.Furthermore, both Sox9 and FBXW7 were detected in immunoblots after the reciprocal protein was immunoprecipitated. Because substrate degradation by SCFFbw7 is typically phosphorylation-dependent, frequently by glycogen synthase kinase (GSK)3-beta, we examined whether modulation of GSK3-beta could affect FBXW7-induced Sox9 degradation. Treatment of cells with the GSK3-beta inhibitor, CHIR99021, completely abolished Sox9 degradation by ectopically overexpressed FBXW7, in a dose-dependent manner. We next identified four putative phosphorylation sites within potential FBXW7 degron motifs in Sox9.Mass spectrophotometric analysis confirmed these sites within Sox9 are indeed phosphorylated.In summary, we found that the E3 ubiquitin ligase complex (SCFFbw7) targets Sox9 for ubiquitin-mediated degradation in a GSK3-beta-mediated Sox9 phosphorylation-dependent manner. As a result, this negative regulation of Sox9 by GSK3-beta/FBXW7 could lead to inhibition of Sox9-mediated proliferation, EMT and stemness. This new regulatory mechanism of Sox9 could have diagnostic and therapeutic implications for lung cancer, osteosarcoma, as well as other cancers.

Citation Format: Xuehui Hong, Wenyu Liu, Hiroyuki Inuzuka, Lianxin Liu, Sharon R. Pine. Negative regulation of Sox9 by glycogen synthase kinase 3 beta phosphorylation and SCFFbw7-dependent ubiquitination in cancer. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 1957. doi:10.1158/1538-7445.AM2015-1957

Abstract 2535: Synergistic anti-tumor activity of the Notch gamma secretase inhibitor BMS-906024 and paclitaxel in the treatment of lung adenocarcinoma

Notch signaling is aberrantly activated in approximately one third of non-small cell lung cancer cases, primarily through loss of the endogenous Notch inhibitor, Numb, or via gain-of-function mutations in the Notch1 receptor. Notch activity is associated with poor overall survival among non-small cell lung cancer patients whose tumors are wildtype for TP53. We set out to evaluate the combination of Notch-targeted therapy with front-line chemotherapy as an effective treatment for non-small cell lung cancer. Our study focused on lung adenocarcinoma, the most common histological subtype in lung cancer. To target Notch, we utilized the gamma secretase inhibitor (GSI) BMS-906024 which inhibits Notch activation. BMS-906024 is currently in Phase 1 clinical trials for patients with T-cell acute lymphoblastic leukemia and metastatic solid tumors, including lung cancer. Human cell lines representing the major genetic subtypes of lung cancer, most of which were derived from adenocarcinomas, underwent MTS drug synergy assays consisting of treatment with BMS-906024, cisplatin or paclitaxel, or the combination of GSI and chemotherapy. The dosing and timing for BMS-906024 administration were optimized by examination of maximal Notch1 inhibition. Analysis of the drug effects with CalcuSyn yielded Combination Index (CI) values, in which a CI of 0.5 or less was considered as strong synergism for the drug combination. We found that there were significantly lower CI values for the GSI BMS-906024 combined with paclitaxel than with cisplatin (average CI = 0.54 vs 0.85, respectively; P = 0.001). We then grouped the cell lines by major genetic subtype (wildtype versus mutant or null for EGFR, Kras or TP53). The synergy between BMS-906024 and paclitaxel was significantly greater in Kras-wildtype than Kras-mutant cells (average CI = 0.39 vs 0.68, respectively; P = 0.009), while there was no correlation with EGFR or TP53 status. These results are a step toward identification of potential biomarkers that could be used to predict patient response to Notch-targeted therapy, which could have a positive impact on the care of lung adenocarcinoma patients and be informative for treatment decisions.

Citation Format: Katherine M. Morgan, Francis Lee, Erin Michaud, Joseph R. Bertino, Bruce S. Fischer, Sharon R. Pine. Synergistic anti-tumor activity of the Notch gamma secretase inhibitor BMS-906024 and paclitaxel in the treatment of lung adenocarcinoma. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 2535. doi:10.1158/1538-7445.AM2015-2535

Sox9 mediates Notch1-induced mesenchymal features in lung adenocarcinoma

Sox9 has gained increasing importance both functionally and as a prognostic factor in cancer. We demonstrate a functional role for Sox9 in inducing a mesenchymal phenotype in lung ADC. We show that Sox9 mRNA and protein are overexpressed in lung ADC, particularly those with KRAS mutations. Sox9 expression correlated with the Notch target gene Hes1, and numerous other Notch pathway components. We observed that Sox9 is a potent inducer of lung cancer cell motility and invasion, and a negative regulator of E-cadherin, a key protein that is lost during epithelial-mesenchymal transition (EMT). Moreover, we show that Notch1 signaling directly regulates Sox9 expression through a SOX9 promoter binding site, independently of the TGF-β pathway, and that Sox9 participates in Notch-1 induced cell motility, cell invasion, and loss of E-cadherin expression. Together, the results identify a new functional role for a Notch1-Sox9 signaling axis in lung ADC that may explain the correlation of Sox9 with tumor progression, higher tumor grade, and poor lung cancer survival. In addition to Notch and TGF-β, Sox9 also acts downstream of NF-κB, BMP, EGFR, and Wnt/β-catenin signaling. Thus, Sox9 could potentially act as a hub to mediate cross-talk among key oncogenic pathways in lung ADC. Targeting Sox9 expression or transcriptional activity could potentially reduce resistance to targeted therapy for lung ADC caused by pathway redundancy.

Identification of a functional SNP in the 3'UTR of CXCR2 that is associated with reduced risk of lung cancer

Global changes in gene expression accompany the development of cancer. Thus, inherited variants in miRNA-binding sites are likely candidates for conferring inherited susceptibility. Using an in silico approach, we compiled a comprehensive list of SNPs predicted to modulate miRNA binding in genes from several key lung cancer pathways. We then investigated whether these SNPs were associated with lung cancer risk in two independent populations. In general, SNPs in miRNA-binding sites are rare. However, some allelic variation was observed. We found that rs1126579 in CXCR2 was associated with a reduced risk of lung cancer in both European American [ORTT vs. CC 0.56 (0.37-0.88); P = 0.008] and Japanese [ORTT vs. CC 0.62 (0.38-1.00); P = 0.049] populations. Furthermore, we found that the SNP disrupted a novel binding site for miR-516a-3p, led to a moderate increase in CXCR2 mRNA and protein expression, and increased MAPK signaling. Moreover, analysis of rs1126579 with serum levels of IL8, its endogenous ligand, supported an interaction whereby rs1126579-T and high serum IL8 conferred synergistic protection from lung cancer. Our findings demonstrate a function for a 3'UTR SNP in modulating CXCR2 expression, signaling, and susceptibility to lung cancer.

A combined prognostic serum interleukin-8 and interleukin-6 classifier for stage 1 lung cancer in the prostate, lung, colorectal, and ovarian cancer screening trial

BACKGROUND

The advent of low-dose helical computed tomography for lung cancer screening will likely lead to an increase in the detection of stage I lung cancer. Presently, these patients are primarily treated with surgery alone and approximately 30% will develop recurrence and die. Biomarkers that can identify patients for whom adjuvant chemotherapy would be a benefit could significantly reduce both patient morbidity and mortality. Herein, we sought to build a prognostic inflammatory-based classifier for stage I lung cancer.

METHODS

We performed a retrospective analysis of 548 European American lung cancer cases prospectively enrolled in the Prostate, Lung, Colorectal and Ovarian study. C-reactive protein, interleukin (IL)-6, IL-8, tumor necrosis factor-α, and IL-1β were measured using an ultrasensitive electrochemiluminescence immunoassay in serum samples collected at the time of study entry.

RESULTS

IL-6 and IL-8 were each associated with significantly shorter survival (hazard ratio [HR], 1.33; 95% confidence interval [CI], 1.08-1.64; p = 0.007; and HR, 1.3; 95% CI, 1.09-1.67; p = 0.005, respectively). Moreover, a combined classifier of IL-6 and IL-8 were significantly associated with poor outcome in stage I lung cancer patients (HR, 3.39; 95% CI, 1.54-7.48, p = 0.002) and in stage 1 patients with more than or equal to 30 pack-years of smoking (HR, 3.15; 95% CI, 1.54-6.46, p = 0.002).

CONCLUSIONS

These results further support the association between inflammatory markers and lung cancer outcome and suggest that a combined serum IL-6/IL-8 classifier could be a useful tool for guiding therapeutic decisions in patients with stage I lung cancer.

Abstract 1149: The role of the novel Notch1-Sox9 signaling axis in NSCLC progression and EMT

Sox9 plays critical roles in the specification and differentiation of numerous progenitor and differentiated cell types during embryonic and fetal development. Sox9 is overexpressed in 40 - 50% of lung adenocarcinomas and associated with poor prognosis in lung cancer patients. We set out to identify upstream pathways that regulate Sox9 expression in lung cancer, as well as the role of Sox9 in lung adenocarcinoma progression. Several developmental and stem cell pathways are known to induce Sox9 transcription during carcinogenesis, including the TGB-β, Wnt/β-catenin, Sonic Hedgehog, and NF-κB signaling. Sox9 has also been shown to be a transcriptional target of the Notch pathway during mouse development, although the binding sites for Notch within the mouse Sox9 promoter are not conserved in humans. We mined gene expression data from three publicly available datasets and found that Hes1, a known Notch target gene, is co-expressed with Sox9 in lung adenocarcinoma. Furthermore, Sox9 mRNA and protein levels were upregulated over 100-fold as early as 14 days after Notch1 induction in the Notch1-induced mouse model of lung cancer, suggesting that Sox9 overexpression is an early event during lung cancer development. Through a series of in vitro assays, we determined that Sox9 is downstream of Notch1 in lung adenocarcinoma cell lines. By ChIP we determined that Sox9 is a direct target of Notch1 and using luciferase reporter assays, we located the previously unidentified human RBP-Jκ binding site, the principle effector of canonical Notch1 signaling, immediately upstream of the Sox9 transcriptional start site. We also examined TGF-β, a known inducer of epithelial-to-mesenchymal transition (EMT) in lung cancer. We determined that induction of Sox9 expression by Notch1 is independent of TGF-β signaling and that TGF-β and Notch1 cooperate in their regulation of Sox9 expression. Loss of Notch1 expression led to an induced MET phenotype, characterized by decreased cell invasion/migration, MET-like morphological changes, and increased E-cadherin expression, which were rescued by Sox9 overexpression. Our data also demonstrate that Sox9 contributes to Notch1-induced EMT in lung adenocarcinoma. These results establish Sox9 as a key Notch1 target gene mediating Notch1-induced EMT independent of TGF-β, leading to poor survival in lung adenocarcinoma.

Citation Format: Kathleen M. Capaccione, Xuehui Hong, Katherine M. Morgan, Thaddeus D. Allen, Gregory D. Miles, Elke K. Markert, J. Michael Bishop, Sharon R. Pine. The role of the novel Notch1-Sox9 signaling axis in NSCLC progression and EMT. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 1149. doi:10.1158/1538-7445.AM2014-1149

Asymmetric cell division and template DNA co-segregation in cancer stem cells

During tissue homeostasis, normal stem cells self-renew and repopulate the diverse cell types found within the tissue via a series of carefully controlled symmetric and asymmetric cell divisions (ACDs). The notion that solid tumors comprise a subset of cancer stem cells (CSCs) with dysregulated self-renewal and excessive symmetric cell divisions has led to numerous studies aimed to elucidate the mechanisms regulating ACD under steady-state conditions, during stem-cell expansion and in cancer. In this perspective, we focus on a type of asymmetry that can be established during ACD, called non-random co-segregation of template DNA, which has been identified across numerous species, cell types, and cancers. We discuss the role of p53 loss in maintaining self-renewal in both normal and malignant cells. We then review our current knowledge of the mechanisms underlying co-segregation of template DNA strands and the stem-cell pathways associated with it in normal and CSCs.

Abstract B17: Sox9 mediates Notch pathway-induced epithelial-mesenchymal transition (EMT) in lung adenocarcinoma

Background: Sox9 plays critical roles in the specification and differentiation of numerous progenitor and differentiated cell types during embryonic and fetal development. Sox9 is overexpressed in 40 - 50% of lung adenocarcinomas and associated with poor prognosis in lung cancer patients. We set out to identify the upstream pathways that regulate Sox9 expression in lung cancer as well as the role of Sox9 in lung adenocarcinoma progression. Several developmental and stem cell pathways are known induce Sox9 transcription during carcinogenesis, including the TGB-β, Wnt/β-catenin, Sonic Hedgehog, and NF-κB signaling pathways. SOX9 has also been shown to be a transcriptional target of the Notch pathway during mouse development, although the binding sites for Notch within the mouse SOX9 promoter are not conserved in humans.

Results: We mined gene expression data from three publicly available datasets and found that Hes1, a known Notch target gene, is co-expressed with Sox9 in lung adenocarcinoma. We validated the data by identifying significant overlap in Sox9 and Hes1 protein expression levels in a human lung cancer tissue microarray. Furthermore, Sox9 mRNA and protein levels were upregulated over 100-fold as early as 14 days after Notch1 induction in the Notch1-induced mouse model of lung cancer, suggesting that Sox9 overexpression is an early event during lung cancer development. Through a series of in vitro assays, we determined that Sox9 is immediately downstream of Notch1, but not Notch3, in lung adenocarcinoma cell lines. By ChIP and luciferase reporter assays, we located the previously unidentified human RBPjk binding site, the principle effector of canonical Notch1 signaling, immediately upstream of the SOX9 transcriptional start site. We also examined TGF-β, a known inducer of epithelial-to-mesenchymal transition (EMT) in lung cancer. We determined that induction of Sox9 expression by Notch1 is independent of TGF-β signaling, that TGF-β upregulates both Sox9 and Notch1 expression, and that TGF-β and Notch1 cooperate in their regulation of Sox9 expression. Sox9 overexpression led to an induced EMT phenotype, characterized by increased cell invasion/migration, and EMT-related gene expression changes. Sox9 mRNA expression correlated with EMT-like gene expression signatures in several gene expression microarray datasets, and Sox9 protein levels were negatively correlated with expression of the epithelial marker, E-cadherin, in a lung cancer tissue microarray. Our data also demonstrate that Notch1-induced EMT in lung adenocarcinoma is mediated, at least partly, through Sox9.

Conclusion: These results establish Sox9 as a key Notch1 target gene mediating Notch1- and TGF-β- induced EMT, leading to poor survival in lung adenocarcinoma.

Citation Format: Kathleen Capaccione, Xuehui Hong, Katherine M. Morgan, Wenyu Liu, Thaddeus Allen, J. Michael Bishop, Sharon R. Pine. Sox9 mediates Notch pathway-induced epithelial-mesenchymal transition (EMT) in lung adenocarcinoma. [abstract]. In: Proceedings of the AACR-IASLC Joint Conference on Molecular Origins of Lung Cancer; 2014 Jan 6-9; San Diego, CA. Philadelphia (PA): AACR; Clin Cancer Res 2014;20(2Suppl):Abstract nr B17.

p53 isoforms regulate aging- and tumor-associated replicative senescence in T lymphocytes

Cellular senescence contributes to aging and decline in tissue function. p53 isoform switching regulates replicative senescence in cultured fibroblasts and is associated with tumor progression. Here, we found that the endogenous p53 isoforms Δ133p53 and p53β are physiological regulators of proliferation and senescence in human T lymphocytes in vivo. Peripheral blood CD8+ T lymphocytes collected from healthy donors displayed an age-dependent accumulation of senescent cells (CD28-CD57+) with decreased Δ133p53 and increased p53β expression. Human lung tumor-associated CD8+ T lymphocytes also harbored senescent cells. Cultured CD8+ blood T lymphocytes underwent replicative senescence that was associated with loss of CD28 and Δ133p53 protein. In poorly proliferative, Δ133p53-low CD8+CD28- cells, reconstituted expression of either Δ133p53 or CD28 upregulated endogenous expression of each other, which restored cell proliferation, extended replicative lifespan and rescued senescence phenotypes. Conversely, Δ133p53 knockdown or p53β overexpression in CD8+CD28+ cells inhibited cell proliferation and induced senescence. This study establishes a role for Δ133p53 and p53β in regulation of cellular proliferation and senescence in vivo. Furthermore, Δ133p53-induced restoration of cellular replicative potential may lead to a new therapeutic paradigm for treating immunosenescence disorders, including those associated with aging, cancer, autoimmune diseases, and HIV infection.

Asymmetric segregation of template DNA strands in basal-like human breast cancer cell lines

BACKGROUND AND METHODS

Stem or progenitor cells from healthy tissues have the capacity to co-segregate their template DNA strands during mitosis. Here, we set out to test whether breast cancer cell lines also possess the ability to asymmetrically segregate their template DNA strands via non-random chromosome co-segregation, and whether this ability correlates with certain properties attributed to breast cancer stem cells (CSCs). We quantified the frequency of asymmetric segregation of template DNA strands in 12 human breast cancer cell lines, and correlated the frequency to molecular subtype, CD44+/CD24-/lo phenotype, and invasion/migration ability. We tested if co-culture with human mesenchymal stem cells, which are known to increase self-renewal, can alter the frequency of asymmetric segregation of template DNA in breast cancer.

RESULTS

We found a positive correlation between asymmetric segregation of template DNA and the breast cancer basal-like and claudin-low subtypes. There was an inverse correlation between asymmetric segregation of template DNA and Her2 expression. Breast cancer samples with evidence of asymmetric segregation of template DNA had significantly increased invasion and borderline significantly increased migration abilities. Samples with high CD44+/CD24-/lo surface expression were more likely to harbor a consistent population of cells that asymmetrically segregated its template DNA; however, symmetric self-renewal was enriched in the CD44+/CD24-/lo population. Co-culturing breast cancer cells with human mesenchymal stem cells expanded the breast CSC pool and decreased the frequency of asymmetric segregation of template DNA.

CONCLUSIONS

Breast cancer cells within the basal-like subtype can asymmetrically segregate their template DNA strands through non-random chromosome segregation. The frequency of asymmetric segregation of template DNA can be modulated by external factors that influence expansion or self-renewal of CSC populations. Future studies to uncover the underlying mechanisms driving asymmetric segregation of template DNA and dictating cell fate at the time of cell division may explain how CSCs are maintained in tumors.

The Notch signaling pathway as a mediator of tumor survival

The Notch signaling pathway is evolutionarily conserved and responsible for cell fate determination in the developing embryo and mature tissue. At the molecular level, ligand binding activates Notch signaling by liberating the Notch intracellular domain, which then translocates into the nucleus and activates gene transcription. Despite the elegant simplicity of this pathway, which lacks secondary messengers or a signaling cascade, Notch regulates gene expression in a highly context- and cell-type-dependent manner. Notch signaling is frequently dysregulated, most commonly by overactivation, across many cancers and confers a survival advantage on tumors, leading to poorer outcomes for patients. Recent studies demonstrate how Notch signaling increases tumor cell proliferation and provide evidence that active Notch signaling maintains the cancer stem-cell pool, induces epithelial-mesenchymal transition and promotes chemoresistance. These studies imply that pharmacological inhibition of Notch signaling may refine control of cancer therapy and improve patient survival. Gamma secretase inhibitors (GSIs) are drugs that inhibit Notch signaling and may be successful in controlling cancer cell growth in conjunction with standard chemotherapy, but substantial side effects have hampered their widespread use. Recent efforts have been aimed at the development of antibodies against specific Notch receptors and ligands with the hope of limiting side effects while providing the same therapeutic benefit as GSIs. Together, studies characterizing Notch signaling and modulation have offered hope that refined methods targeting Notch may become powerful tools in anticancer therapeutics.

Delineation of breast cancer cell hierarchy identifies the subset responsible for dormancy

The bone marrow (BM) is a major organ of breast cancer (BC) dormancy and a common source of BC resurgence. Gap junctional intercellular communication (GJIC) between BC cells (BCCs) and BM stroma facilitates dormancy. This study reports on a hierarchy of BCCs with the most immature subset (Oct4^hi/CD44^hi/med/CD24^−/+) demonstrating chemoresistance, dormancy, and stem cell properties: self-renewal, serial passaging ability, cycling quiescence, long doubling time, asymmetric division, high metastatic and invasive capability. In vitro and in vivo studies indicated that this subset was responsible for GJIC with BM stroma. Similar BCCs were detected in the blood of patients despite aggressive treatment and in a patient with a relatively large tumor but no lymph node involvement. In brief, these findings identified a novel BCC subset with stem cell properties, with preference for dormancy and in the circulation of patients. The findings establish a working cellular hierarchy of BCCs based on phenotype and functions.

MDM2 SNP285 does not antagonize the effect of SNP309 in lung cancer

Conflicting reports exist regarding the contribution of SNP309 in MDM2 to cancer risk. Recently, SNP285 was shown to act as an antagonist to SNP309 by overriding the effect of SNP309 on SP1-mediated transcription. Moreover, SNP285 modified the relationship between SNP309 and risk of breast, ovarian and endometrial cancer. We assessed whether SNP285 confounded the effect of SNP309 in lung cancer in a cohort of 720 controls and 556 cases. Our cohort included both Caucasians and African Americans. Neither SNP309 nor SNP285 was associated with lung cancer risk or survival. In addition, removal of individuals who carried the variant C allele of SNP285 did not modify the association between SNP309 with either lung cancer risk or survival. Although an effect of SNP285 has been demonstrated in breast, ovarian and endometrial cancer, our findings do not support a role for this SNP in lung cancer and raise the possibility that the effect of SNP285 is restricted to cancers in women.

Abstract B1: p53 isoforms, Δ133p53 and p53β, regulate aging-associated T lymphocyte senescence

Normal human cells undergo finite divisions and reach a state of cellular senescence, which is a critical barrier for tumor progression in vivo and contributes to organismal aging. CD8+ T lymphocytes are an excellent model to study cellular senescence in vivo. The decreased proliferative potential and cellular senescence of CD8+ T lymphocytes are associated with loss of CD28 and gain of CD57 cell surface antigens, but the mechanisms regulating these phenotypic changes are unknown. The natural isoforms of human p53 protein, Δ133p53 and p53β, play important roles in regulating replicative cellular senescence in vitro (e.g., in normal human fibroblasts) and in vivo (e.g., in colon adenomas) and in different cell types (mesenchymal and epithelial origins). In this study we show that Δ133p53 and p53β are associated with and regulate replicative cellular senescence in CD8+ T lymphocytes (hematopoietic origin), which represent a physiological setting of in vivo cellular senescence. Loss of CD28 and gain of CD57 in CD8+ T lymphocytes were associated with increased donor age in normal individuals. When stimulated to proliferate in vitro, the FACS sorted CD28+/CD57− subsets of CD8+ T lymphocytes showed highest proliferation rate, whereas CD28−/CD57+ subsets showed lowest. The loss of proliferative potential of the CD28−/CD57+ cells was also associated with the shorter telomere length than the CD28+/CD57− subsets. Importantly, Δ133p53 and p53β expression levels were significantly changed during cellular senescence of CD8+ T lymphocytes, as observed in human fibroblasts and colon adenomas. Δ133p53 levels were decreased and p53β levels were increased in the senescent CD28−/CD57+ subset compared with the proliferative CD28+/CD57− subset. During in vitro culture, FACS sorted CD8+ T lymphocytes became senescent and lost Δ133p53 expression, which was associated with the loss of CD28 expression. Moreover, in overexpression experiments, p53β cooperated with full-length p53 to inhibit cellular proliferation, and Δ133p53 enhanced the proliferative potential of the CD8+ T lymphocytes, suggesting that the p53 isoforms regulate cellular proliferation and senescence in CD8+ T lymphocytes. Our study provides insight toward understanding the mechanisms regulating physiological aging of normal human circulating T lymphocytes and thus proposes a novel approach for reinstating replicative potential and immune function of the senescent CD8+ T lymphocytes.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the Second AACR International Conference on Frontiers in Basic Cancer Research; 2011 Sep 14-18; San Francisco, CA. Philadelphia (PA): AACR; Cancer Res 2011;71(18 Suppl):Abstract nr B1.

Increased levels of circulating interleukin 6, interleukin 8, C-reactive protein, and risk of lung cancer

BACKGROUND

Previous studies that were based primarily on small numbers of patients suggested that certain circulating proinflammatory cytokines may be associated with lung cancer; however, large independent studies are lacking.

METHODS

Associations between serum interleukin 6 (IL-6) and interleukin 8 (IL-8) levels and lung cancer were analyzed among 270 case patients and 296 control subjects participating in the National Cancer Institute-Maryland (NCI-MD) case-control study. Results were validated in 532 case patients and 595 control subjects in a nested case-control study within the prospective Prostate, Lung, Colorectal, and Ovarian (PLCO) Cancer Screening Trial. Association with C-reactive protein (CRP), a systemic inflammation biomarker, was also analyzed. Associations between biomarkers and lung cancer were estimated using logistic regression models adjusted for smoking, stage, histology, age, and sex. The 10-year standardized absolute risks of lung cancer were estimated using a weighted Cox regression model.

RESULTS

Serum IL-6 and IL-8 levels in the highest quartile were associated with lung cancer in the NCI-MD study (IL-6, odds ratio [OR] = 3.29, 95% confidence interval [CI] = 1.88 to 5.77; IL-8, OR = 2.06, 95% CI = 1.19 to 3.57) and with lung cancer risk in the PLCO study (IL-6, OR = 1.48, 95% CI = 1.04 to 2.10; IL-8, OR = 1.57, 95% CI = 1.10 to 2.24), compared with the lowest quartile. In the PLCO study, increased IL-6 levels were only associated with lung cancer diagnosed within 2 years of blood collection, whereas increased IL-8 levels were associated with lung cancer diagnosed more than 2 years after blood collection (OR = 1.57, 95% CI = 1.15 to 2.13). The 10-year standardized absolute risks of lung cancer in the PLCO study were highest among current smokers with high IL-8 and CRP levels (absolute risk = 8.01%, 95% CI = 5.77% to 11.05%).

CONCLUSIONS

Although increased levels of both serum IL-6 and IL-8 are associated with lung cancer, only IL-8 levels are associated with lung cancer risk several years before diagnosis. Combination of IL-8 and CRP are more robust biomarkers than either marker alone in predicting subsequent lung cancer.

Admixture mapping of lung cancer in 1812 African-Americans

Lung cancer continues to be the leading cause of cancer death in the USA and the best example of a cancer with undisputed evidence of environmental risk. However, a genetic contribution to lung cancer has also been demonstrated by studies of familial aggregation, family-based linkage, candidate gene studies and most recently genome-wide association studies (GWAS). The African-American population has been underrepresented in these genetic studies and has patterns of cigarette use and linkage disequilibrium that differ from patterns in other populations. Therefore, studies in African-Americans can provide complementary data to localize lung cancer susceptibility genes and explore smoking dependence-related genes. We used admixture mapping to further characterize genetic risk of lung cancer in a series of 837 African-American lung cancer cases and 975 African-American controls genotyped at 1344 ancestry informative single-nucleotide polymorphisms. Both case-only and case-control analyses were conducted using ADMIXMAP adjusted for age, sex, pack-years of smoking, family history of lung cancer, history of emphysema and study site. In case-only analyses, excess European ancestry was observed over a wide region on chromosome 1 with the largest excess seen at rs6587361 for non-small-cell lung cancer (NSCLC) (Z-score = -4.33; P = 1.5 × 10⁻⁵) and for women with NSCLC (Z-score = -4.82; P = 1.4 × 10⁻⁶). Excess African ancestry was also observed on chromosome 3q with a peak Z-score of 3.33 (P = 0.0009) at rs181696 among ever smokers with NSCLC. These results add to the findings from the GWAS in Caucasian populations and suggest novel regions of interest.

C-reactive protein and risk of lung cancer

PURPOSE

Chronic inflammation could play a role in lung carcinogenesis, underscoring the potential for lung cancer prevention and screening. We investigated the association of circulating high-sensitivity C-reactive protein (CRP, an inflammation biomarker) and CRP single nucleotide polymorphisms (SNPs) with prospective lung cancer risk.

PATIENTS AND METHODS

We conducted a nested case-control study of 592 lung cancer patients and 670 controls with available prediagnostic serum and 378 patients and 447 controls with DNA within the screening arm of the Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial (N = 77,464). Controls were matched to patients on age, sex, entry year, follow-up time, and smoking. We measured CRP levels in baseline serum samples and genotyped five common CRP SNPs.

RESULTS

Elevated CRP levels were associated with increased lung cancer risk (odds ratio [OR], 1.98; 95% CI, 1.35 to 2.89; P-trend < .001 for fourth quartile [Q4, > or = 5.6 mg/L] v Q1 [< 1.0 mg/L]). The CRP association did not differ significantly by histology, follow-up time, or smoking status, but was most apparent for squamous cell carcinomas (OR, 2.92; 95% CI, 1.30 to 6.54), 2 to 5 years before lung cancer diagnosis (OR, 2.33; 95% CI, 1.24 to 4.39), and among former smokers (OR, 2.48; 95% CI, 1.53 to 4.03) and current smokers (OR, 1.90; 95% CI, 1.06 to 3.41). Although CRP SNPs and haplotypes were associated with CRP levels, they were not associated with lung cancer risk. Ten-year standardized absolute risks of lung cancer were higher with elevated CRP levels among former smokers (Q4: 2.55%; 95% CI, 1.98% to 3.27% v Q1: 1.39%; 95% CI, 1.07% to 1.81%) and current smokers (Q4: 7.37%; 95% CI, 5.81% to 9.33% v Q1: 4.03%; 95% CI, 3.01% to 5.40%).

CONCLUSION

Elevated CRP levels are associated with subsequently increased lung cancer risk, suggesting an etiologic role for chronic pulmonary inflammation in lung carcinogenesis.

Abstract 4238: Human non-small cell lung cancer cells asymmetrically divide their template DNA strands and cell fate proteins

Certain subpopulations of tumor cells are capable of both self-renewal and regeneration of phenotypically heterogeneous tumors. These observations suggest that tumor initiation and maintenance are linked to asymmetric cell divisions of tumor stem cells. However, cell progeny of symmetric divisions could adopt different cell fates, possibly through interactions between the daughter cells and their microenvironments. We set out to determine if human lung cancer primary tumor cells and cell lines asymmetrically divide their template DNA strands exclusively to only one daughter cell during cell division, and further, if the process is linked to cell fate. By performing pulse-chase experiments with halogenated thymidine analogs, we observed that 0.7-6.0% of cells within human lung cancer cell lines and 15-25% of short-term culture cells from primary lung tumor samples asymmetrically divide their template DNA strands. The data was confirmed by examination of asymmetrically dividing cells by two-color DNA analogs and visualization in real-time. Furthermore, cells that asymmetrically divide the lung cancer stem cell marker CD133 are 10-fold more likely to asymmetrically divide their labeled template DNA strands than cells that symmetrically divide CD133, and in each case, the CD133 co-segregates with the older DNA strands. The lung adenocarcinoma differentiation marker pro-surfactant protein C (SPC) is passed to the opposing daughter cell in 93% of cell divisions that asymmetrically divide both the DNA and SPC, suggesting a correlation between asymmetric division of template DNA and cell fate. To gain insight into the mechanisms regulating asymmetric cell division in lung cancer, we subjected cell lines to conditions known to enhance self-renewal. We observed that the frequency of template DNA co-segregation decreases 2- to 3-fold at lower cell densities as well as during serum deprivation and hypoxic conditions. These data indicate that a switch from asymmetric to symmetric cell divisions is one mechanism by which tumor cells increase self-renewal. Furthermore, the process requires cell-cell contact, suggesting that the niche participating in self-renewal regulation is provided by direct signaling from neighboring tumor cells. Our results demonstrate that a hierarchical cellular pattern within human lung tumors may be regulated, in part, by an orchestrated mechanism of self-renewal and differentiation involving co-segregation of template DNA and cell fate markers. An in-depth examination of intercellular and environmental response signaling pathways are needed to decipher exactly how neighboring cells and the environment influence cancer cell fate decisions. Examination of genes known to disrupt asymmetric cell division in lower organisms in human cancers could elucidate novel pathways controlling cancer maintenance and provide novel therapeutic targets.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 4238.

Abstract 2915: p53 isoforms Δ133p53 and p53β are endogenous regulators of replicative cellular senescence

The finite proliferative potential of normal human cells leads to replicative cellular senescence, which is a critical barrier to tumor progression in vivo. The p53 signaling pathway plays central roles in the regulation of cellular senescence. Humans, as well as Drosophila and zebrafish, have p53 isoforms; however, their regulation and function are poorly understood. We here examine the expression profiles of two human p53 isoforms, p53β (lacking the C-terminal oligomerization domain due to an alternative mRNA splicing) and Δ133p53 (lacking the N-terminal transactivation and proline-rich domains due to the transcription from an alternative promoter in intron 4), during in vitro and in vivo cellular senescence and their biological activities in regulating cellular senescence. Induced p53β and diminished Δ133p53 were associated with replicative senescence, but not oncogene-induced senescence, in normal human fibroblasts. The replicatively senescent fibroblasts also expressed increased levels of miR-34a, a p53-induced microRNA, the antisense inhibition of which delayed the onset of replicative senescence. The siRNA-mediated knockdown of endogenous Δ133p53 induced cellular senescence, which was attributed to the regulation of p21WAF1 and other p53 transcriptional target genes. In overexpression experiments, while p53β cooperated with full-length p53 to accelerate cellular senescence, Δ133p53 repressed miR-34a expression and extended cellular replicative lifespan, providing a functional connection of this microRNA to the p53 isoform-mediated regulation of senescence. The senescence-associated signature of p53 isoform expression (i.e., elevated p53β and reduced Δ133p53) was observed in vivo in colon adenomas with senescent phenotypes. The decreased p53β and increased Δ133p53 expression found in colon carcinomas might signal an escape from the senescence barrier during the progression from premalignant to malignant tumors in vivo. This study shows that natural p53 isoforms constitute an endogenous regulatory mechanism for p53-mediated replicative senescence and may open up a new p53-based, senescence-mediated strategy to manipulate carcinogenesis and aging. The molecular details of the senescence-associated Δ133p53 repression and p53β induction are currently under investigation.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 2915.

Childhood exposure to secondhand smoke and functional mannose binding lectin polymorphisms are associated with increased lung cancer risk

BACKGROUND

Exposure to secondhand smoke during adulthood has detrimental health effects, including increased lung cancer risk. Compared with adults, children may be more susceptible to secondhand smoke. This susceptibility may be exacerbated by alterations in inherited genetic variants of innate immunity genes. We hypothesized a positive association between childhood secondhand smoke exposure and lung cancer risk that would be modified by genetic polymorphisms in the mannose binding lectin-2 (MBL2) gene resulting in well-known functional changes in innate immunity.

METHODS

Childhood secondhand smoke exposure and lung cancer risk was assessed among men and women in the ongoing National Cancer Institute-Maryland Lung Cancer (NCI-MD) study, which included 624 cases and 348 controls. Secondhand smoke history was collected via in-person interviews. DNA was used for genotyping the MBL2 gene. To replicate, we used an independent case-control study from Mayo Clinic consisting of 461 never smokers, made up of 172 cases and 289 controls. All statistical tests were two-sided.

RESULTS

In the NCI-MD study, secondhand smoke exposure during childhood was associated with increased lung cancer risk among never smokers [odds ratio (OR), 2.25; 95% confidence interval (95% CI), 1.04-4.90]. This was confirmed in the Mayo study (OR, 1.47; 95% CI, 1.00-2.15). A functional MBL2 haplotype associated with high circulating levels of MBL and increased MBL2 activity was associated with increased lung cancer risk among those exposed to childhood secondhand smoke in both the NCI-MD and Mayo studies (OR, 2.52; 95% CI, 1.13-5.60, and OR, 2.78; 95% CI, 1.18-3.85, respectively).

CONCLUSIONS

Secondhand smoke exposure during childhood is associated with increased lung cancer risk among never smokers, particularly among those possessing a haplotype corresponding to a known overactive complement pathway of the innate immune system.