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Lung cancer is the leading cause of cancer-related mortality worldwide. Early detection is essential to achieving a better outcome and prognosis. Volatile organic compounds (VOCs) reflect alterations in the pathophysiology and body metabolism processes, as shown in various types of cancers. The biosensor platform (BSP) urine test uses animals’ unique, proficient, and accurate ability to scent lung cancer VOCs. The BSP is a testing platform for the binary (negative/positive) recognition of the signature VOCs of lung cancer by trained and qualified Long–Evans rats as biosensors (BSs). The results of the current double-blind study show high accuracy in lung cancer VOC recognition, with 93% sensitivity and 91% specificity. The BSP test is safe, rapid, objective and can be performed repetitively, enabling periodic cancer monitoring as well as an aid to existing diagnostic methods. The future implementation of such urine tests as routine screening and monitoring tools has the potential to significantly increase detection rate as well as curability rates with lower healthcare expenditure. This paper offers a first instructive clinical platform utilizing VOC’s in urine for detection of lung cancer using the innovative BSP to deal with the pressing need for an early lung cancer detection test tool.

Supplementary Fig. S1: Identification of primary fibroblasts isolated from freshly resected lung tumors (CAFs). Supplementary Fig. S2: Kinetics of MDM2 protein elevation by H1299-CM. Supplementary Fig. S3: Cancer-CMs induce elevation in normal and cancer-associated fibroblasts from lung adenocarcinoma and squamous cell carcinoma. Supplementary Fig. S4: Variable elevation of stromal-MDM2 by cancer-CMs. Supplementary Fig. S5: Cancer-CM's species-specific effect. Supplementary Fig. S6: Lung CAFs induce cancer cells' invasion, which is attenuated by both Rapamycin and by knockdown of MDM2 in CAFs. Supplementary Fig. S7: MDM2-dependent pro-invasion effect is p53-independent. Supplementary Fig. S8: In vivo detected tumors are originated from H1299 epithelial cells.

Supplementary Data from Differential Influence of Normal and Cancer-Associated Fibroblasts on the Growth of Human Epithelial Cells in an In vitro Cocultivation Model of Prostate Cancer

The prostate is composed of a number of different cell populations. The interaction between them is crucial for the development and proper function of the prostate. However, the effect of the molecular cross talk between these cells in the course of carcinogenesis is still unclear. Employing an approach wherein immortalized epithelial cells and immortalized human fibroblasts were cocultured, we show that normal associated fibroblasts (NAF) and cancer-associated fibroblasts (CAF) differentially influenced the growth and proliferation of immortalized human prostate epithelial cells. Whereas NAFs inhibited the growth of immortalized epithelial cells but promoted the growth of metastatic PC-3 cells, CAFs promoted the growth of immortalized epithelial cells but not of PC-3. Cytokine arrays revealed that NAFs secreted higher levels of tumor necrosis factor-α compared with CAFs whereas CAFs secreted higher levels of interleukin-6 (IL-6) compared with NAFs. The growth-inhibiting effects of NAFs were counteracted by the addition of IL-6, and the growth-promoting effects exerted by the CAFs were counteracted by tumor necrosis factor-α. Furthermore, CAFs induced the migration of endothelial cells in an IL-6–dependent manner. Here, we show that normal fibroblast cells have a protective function at very early stages of carcinogenesis by preventing immortalized epithelial cells from proliferating and forming new blood vessels whereas CAFs aid immortalized epithelial cells to further develop. (Mol Cancer Res 2009;7(8):1212–23)

Translating preclinical studies to effective treatment protocols and identifying specific therapeutic responses in individuals with cancer is challenging. This may arise due to the complex genetic makeup of tumor cells and the impact of their multifaceted tumor microenvironment on drug response. To find new clinically relevant drug combinations for colorectal cancer (CRC), we prioritized the top five synergistic combinations from a large in vitro screen for ex vivo testing on 29 freshly resected human CRC tumors and found that only the combination of mitogen-activated protein kinase kinase (MEK) and proto-oncogene tyrosine-protein kinase Src (Src) inhibition was effective when tested ex vivo. Pretreatment phosphorylated Src (pSrc) was identified as a predictive biomarker for MEK and Src inhibition only in the absence of KRAS

One of the major hurdles for the advancement of cancer immunotherapy is lack of robust, accessible experimental models. We aimed to produce an ex-vivo organ culture (EVOC) model of immunotherapy for non-small cell lung cancer (NSCLC). Freshly resected early stage tumors were collected from the operating room, fragmented to clusters

Tumor–host interactions play a major role in malignancies' initiation and progression. We have reported in the past that tumor cells attenuate genotoxic stress–induced p53 activation in neighboring stromal cells. Herein, we aim to further elucidate cancer cells' impact on signaling within lung cancer stroma. Primary cancer-associated fibroblasts were grown from resected human lung tumors. Lung cancer lines as well as fresh cultures of resected human lung cancers were used to produce conditioned medium (CM) or cocultured with stromal cells. Invasiveness of cancer cells was evaluated by transwell assays, and in vivo tumor growth was tested in Athymic nude mice. We found CM of a large variety of cancer cell lines as well as ex vivo–cultured lung cancers to rapidly induce protein levels of stromal-MDM2. CM of nontransformed cells had no such effect. Mdm2 induction occurred through enhanced translation, was mTORC1-dependent, and correlated with activation of AKT and p70 S6 Kinase. AKT or MDM2 knockdown in fibroblasts reduced the invasion of neighboring cancer cells, independently of stromal-p53. MDM2 overexpression in fibroblasts enhanced cancer cells' invasion and growth of inoculated tumors in mice. Our results indicate that stromal-MDM2 participates in a p53-independent cancer–host feedback mechanism. Soluble cancer-originated signals induce enhanced translation of stromal-MDM2 through AKT/mTORC1 signaling, which in turn enhances the neighboring cancer cells' invasion ability. The role of these tumor–host interactions needs to be further explored. Implications: We uncovered a novel tumor–stroma signaling loop, which is a potentially new therapeutic target in lung cancer and possibly in additional types of cancer.

Purpose Sleep is essential for life, as well as having a major impact on quality of life. Not much attention has been given to this important factor in the care of lung cancer patients. Patients and methods We retrospectively analyzed a cohort of 404 lung cancer patients treated in our institute between 2010 and 2018. Data about sleep quality, distress and pain were self-reported by questionnaires administered to patients at their first clinic visit to the Institute of Oncology. Sex, age, histology, stage, smoking and marital status were extracted from the patients' charts. Uni- and multi-variate analyses were carried out to evaluate the correlation of these factors with survival. Results Most patients reported some level of distress and pain. Sleep abnormalities were reported by 58.7% of patients. Distress, pain and bad sleep were correlated with shorter survival in univariate analyses; however, only sleep remained associated with survival in multivariate analysis. Patients reporting bad sleep had a median survival of 16 months, compared to 27 months for patients reporting good sleep (hazard ratio 1.83, 95% C.I. 1.27-2.65). Frequent arousals at night were more tightly correlated with survival than difficulty falling asleep. Conclusion Sleep quality, as reported by lung cancer patients, is highly correlated with survival. Further studies are required to comprehend whether poor sleep quality is directly impacting survival or is a result of the cancer aggressiveness and patients' conditions.

Comment in: DePICting T cell-APC crosstalk in cancer. Zhang T, Dong C. Nat Cancer. 2022 Mar;3(3):265-267. doi: 10.1038/s43018-022-00345-6. PMID: 35352059 No abstract available.; International audience; Despite their key regulatory role and therapeutic potency, the molecular signatures of interactions between T cells and antigen-presenting myeloid cells within the tumor microenvironment remain poorly characterized. Here, we systematically characterize these interactions using RNA sequencing of physically interacting cells (PIC-seq) and find that CD4+PD-1+CXCL13+ T cells are a major interacting hub with antigen-presenting cells in the tumor microenvironment of human non-small cell lung carcinoma. We define this clonally expanded, tumor-specific and conserved T-cell subset as T-helper tumor (Tht) cells. Reconstitution of Tht cells in vitro and in an ovalbumin-specific αβ TCR CD4+ T-cell mouse model, shows that the Tht program is primed in tumor-draining lymph nodes by dendritic cells presenting tumor antigens, and that their function is important for harnessing the antitumor response of anti-PD-1 treatment. Our molecular and functional findings support the modulation of Tht-dendritic cell interaction checkpoints as a major interventional strategy in immunotherapy.

BackgroundImmune checkpoint inhibitors (ICIs) have revolutionized cancer treatment by shifting the focus from the tumor to the immune system of the host. Despite durable response to ICIs, only a small proportion of non-small lung cancer (NSCLC) patients respond to this treatment. Thus, great effort is currently focused on uncovering mechanisms of resistance and identifying predictive biomarkers for outcome.MethodsBlood plasma was obtained from 143 NSCLC patients treated with ICI-based therapy at baseline and early on-treatment (following the first treatment), and the levels of approximately 800 proteins were determined using ELISA-based arrays. Bioinformatic analysis was performed in order to detect novel patterns of resistance to ICI-based therapy. To identify a signature that predicts clinical outcome, a machine learning algorithm was applied.ResultsUnsupervised bioinformatic analysis of the plasma proteomic profiles classified the patients into 3 clusters with distinct clinical and biological features. Patients in cluster #1 exhibited resistance to therapy, bone metastasis and high TNM (tumors, nodes and metastasis) staging; this cluster displayed high levels of proteins related to glycan and pyrimidine metabolism and cell-adhesion. Cluster #2 was enriched with responders, males, and patients with low TNM staging; this cluster displayed a strong representation of desmoglein proteins. Cluster #3 was enriched with female patients while the proteome of these patients displayed high levels of MAPK signaling related proteins. Patient clusters were largely unchanged when comparing baseline and on-treatment data, suggesting pre-existing rather than acquired resistance to therapy. A further comparison between responders and non-responders identified six significantly differentially expressed proteins comprised of both host- and tumor-related proteins, with non-responders displaying a significant enrichment of neutrophil proteins at baseline and early-on-treatment. Notably, there was no significant difference in the neutrophil count between responders and non-responders, suggesting a functional shift in neutrophils upon treatment in non-responders. Lastly, we identified a predictive signature for response comprised of two proteins and two clinical features. The performance of the predictive signature reached an area under the curve (AUC) of the receiver operating characteristics (ROC) plot of 0.8 in an independent validation subset of the cohort, indicating a high predictive power.ConclusionsHere we performed a deep bioinformatic analysis of plasma proteome profiles of 143 NSCLC patients undergoing ICI-based therapy. Our study sheds light on underlying mechanisms of resistance to ICI-based therapy and reveals a predictive signature for response in NSCLC patients.Ethics ApprovalData and study specimens were purchased from Indivumed and Sheba medical center, approval number 0226-13-SMC (institutional review board). Participants gave informed consent before taking part.

SummaryProtein degradation by proteasomes is important for the immune response against tumors. Antigens generated by the proteasome promote immune cell infiltration into tumors and improve tumors’ responses to immunotherapy. For example, immunoproteasomes – a subset of proteasomes induced by inflammatory signals – may improve the response of melanomas to immune checkpoint inhibitors (ICI) by eliciting tumor inflammation. Yet, it is unclear whether and how protein degradation by proteasomes impacts cancer progression and contributes to immune evasion and resistance. Here, we profile the proteasome-cleaved peptides in lung cancers and find that PSME4 serves as a novel inhibitory regulator of the immunoproteasome, playing an anti-inflammatory role in cancer. Biochemical assays combined with scRNA-seq, immunopeptidomics and in vivo analyses demonstrate that PSME4 promotes an immunosuppressive environment around the tumor and abrogates anti-tumor immunity by inhibiting antigen presentation and attenuating tumor inflammation. Furthermore, we find that PSME4 expression is correlated with responsiveness to ICI across several cancer types. Our findings suggest that PSME4-mediated regulation of proteasome activity is a novel mechanism of immune evasion in non-small-cell lung carcinoma and may be targeted therapeutically for restoring anti-tumor immunity.Graphical AbstractHighlightsMapping the degradation landscape in Non-Small Cell Lung Cancer (NSCLC) uncovers altered proteasome activity and compositionProteasome regulator PSME4 plays an anti-inflammatory role in NSCLC by attenuating immunoproteasome activityPSME4 restricts tumor antigen presentation and cytokine secretion, defining a ‘cold’ tumor environmentPSME4 drives tumor immune evasion and is associated with resistance to immunotherapy

Despite their key regulatory role and therapeutic potency, the molecular signatures of interactions between T cells and antigen-presenting myeloid cells within the tumor microenvironment remain poorly characterized. Here, we systematically characterize these interactions using RNA sequencing of physically interacting cells (PIC-seq) and find that CD4

Background Neoadjuvant immune checkpoint inhibitor treatment is a promising approach for resectable cancer, including non-small cell lung cancer (NSCLC). The characteristics of potential responders to such treatments and the molecular underlying events are not known. Methods We have conducted a phase I, investigator-initiated single-center study (MK3457-223), to examine the safety of neoadjuvant pembrolizumab for stage I-II resectable NSCLC and to determine the recommended phase II dose/schedule (RP2D/S). FFPE biopsies and surgical specimens were subjected to correlative studies. NanoString’s GeoMx Digital Spatial Profiler (DSP) analysis was conducted on pre-treatment samples and post-treatment responder samples. Protein (72 proteins) and mRNA expression data (73 genes) analysis was conducted on regions of interest (ROIs), defined as mostly CD8 positive or mostly pan-cytokeratin positive (presumed cancer cells). Pathology assessment was done on the surgical specimen to identify major pathologic response (MPR; ≤10% remaining viable cells). Statistical analysis was done to compare responders (MPR+) to non-responders (MPR-) by Mann Whitney with false discovery rate correction. Immunohistochemistry (IHC) was conducted on post-treatment samples. Results Twenty-six patients initiated treatment on the study. Two patients (8%, 95% C.I 0-18%) had adverse events that precluded surgery, 1 patient refused surgery after treatment. 7 patients (27%, 95% C.I 10-44%) achieved a major pathologic response (MPR; responders), 3 patients (12%, 95% C.I 0-24%) achieved complete pathologic response. Responders had a longer interval from treatment to surgery (43 days vs. 36 days, univariate analysis, p-value 0.043). RP2D/S was determined as 2 treatments of 200mg pembrolizumab at 3 week interval, followed by surgery at least 2 weeks later. The expression of several proteins and genes differed between responders and non-responders. Pre-treatment, CD20 protein was the most differentially expressed protein both in in CD8+ (4.7 fold, p=0.002) and in cancer cells (4.8 fold, p=0.001) ROIs, in both cases higher in the responders compared to the non-responders. Comparing pre to post-treatment expression in responding tumors, the protein found to be upregulated to the highest extent following pembrolizumab treatment was CD20 protein (6.2-fold, p=0.001), as was its encoding gene, MS4A1 (2.4-fold, p=0.006). CD20 IHC of post-treatment samples demonstrated tertiary lymphoid structures (TLS) to be more prevalent in responders compared to non-responders (3.2-fold, p Citation Format: Jair Bar, Iris Kamer, Oranit Zadok, Damien Urban, Marina Perelman, Ilanit Redinsky, Aliza Ackerstein, Sameh Daher, Efrat Ofek, Amir Onn, Nona Zeitlin, Alon Ben-Nun, Ran Kremer, Inbal Daniel, Yossef Glantzspiegel, Irit Gat-Viks. B-cell infiltration in lung cancer predicts response to neoadjuvant pembrolizumab [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr CT154.

BackgroundImmune checkpoint inhibitors (ICIs) have revolutionized the cancer therapy landscape due to long-term benefits in patients with advanced metastatic disease. However, robust predictive biomarkers for response are still lacking and treatment resistance is not fully understood.MethodsWe profiled approximately 800 pre-treatment and on-treatment plasma proteins from 143 ICI-treated patients with non-small cell lung cancer (NSCLC) using ELISA-based arrays. Different clinical parameters were collected from the patients including specific mutations, smoking habits, and body mass index, among others. Machine learning algorithms were used to identify a predictive signature for response. Bioinformatics tools were used for the identification of patient subtypes and analysis of differentially expressed proteins and pathways in each response group.ResultsWe identified a predictive signature for response to treatment comprizing two proteins (CXCL8 and CXCL10) and two clinical parameters (age and sex). Bioinformatic analysis of the proteomic profiles identified three distinct patient clusters that correlated with multiple parameters such as response, sex and TNM (tumors, nodes, and metastasis) staging. Patients who did not benefit from ICI therapy exhibited significantly higher plasma levels of several proteins on-treatment, and enrichment in neutrophil-related proteins.ConclusionsOur study reveals potential biomarkers in blood plasma for predicting response to ICI therapy in patients with NSCLC and sheds light on mechanisms underlying therapy resistance.

One of the major hurdles for the advancement of cancer immunotherapy is lack of robust, accessible experimental models. We aimed to produce an ex-vivo organ culture (EVOC) model of immunotherapy for non-small cell lung cancer (NSCLC). Freshly resected early stage tumors were collected from the operating room, fragmented to clusters 450 µm and cultured with fetal calf serum and human autologous serum. The resulting EVOC includes cancer epithelial cells within tumor tissue clusters and immune cells. Original tissue features are reflected in the EVOCs. The response to immune checkpoint inhibitors (ICI) was assessed by IFNγ gene induction. Interestingly, IFNγ EVOC induction was numerically higher when anti-CTLA4 was added to anti-PD-L1 treatment, supporting the notion that anti-CTLA4 impacts cancer partly through tumor-resident immune cells. In parallel, immunohistochemistry (IHC) for key immune-related proteins was performed on the formalin-fixed paraffin embedded (FFPE) corresponding tumors. EVOC IFNγ induction by ICI correlated with basal non-induced IFNγ, CD8, CD4 and FOXP3 mRNA levels within EVOCs and with tumor-FFPE-IHC for CD8 and granzyme B. A weaker correlation was seen with tumor-FFPE-IHC for CD3, CD4, CD68, FOXP3 and tumor-PD-L1. Tertiary lymphoid structure density was also correlated with the ICI response. Our study provides novel data about biomarkers that correlate with ICI-induced response of early stage NSCLC. Retention of the microenvironment and minimal addition of exogenous factors suggest this model to reliably represent the original tumor. The cluster-based EVOC model we describe can provide a valuable, yet simple and widely applicable tool for the study of immunotherapy in NSCLC.

Background Non-small cell lung cancer (NSCLC) is the most common cause of cancer-death due to early metastatic spread, in many cases primarily to the brain. Organ-specific pattern of spread of disease might be driven by the activity of a specific signaling pathway within the primary tumors. We aimed to identify an expression signature of genes and the relevant signaling associated with the development of brain metastasis (BM) after surgical resection of NSCLC. Methods Rapidly frozen NSCLC surgical specimens were procured from tumor banks. RNA was extracted and analyzed by RNA-sequencing (Illumina HiSeq 2500). Clinical parameters and gene expression were examined for differentiating between patients with BM, patients with metastases to sites other than brain, and patients who did not develop metastatic disease at a clinically significant follow up. Principal component analysis and pathway enrichments studies were done. Results A total of 91 patients were included in this study, 32 of which developed BM. Stage of disease at diagnosis (P=0.004) and level of differentiation (P=0.007) were significantly different between BM and control group. We identified a set of 22 genes which correlated specifically with BM, and not with metastasis to other sites. This set achieved 93.4% accuracy (95% CI: 86.2-97.5%), 96.6% specificity and 87.5% sensitivity of correctly identifying BM patients in a leave-one-out internal validation analysis. The oxidative phosphorylation pathway was strongly correlated with BM risk. Conclusions Expression level of a small set of genes from primary tumors was found to predict BM development, distinctly from metastasis to other organs. These genes and the correlated oxidative phosphorylation pathway require further validation as potentially clinically useful predictors of BM and possibly as novel therapeutic targets for BM prevention.

Stochastic transition of cancer cells between drug-sensitive and drug-tolerant persister phenotypes has been proposed to play a key role in non-genetic resistance to therapy. Yet, we show here that cancer cells actually possess a highly stable inherited chance to persist (CTP) during therapy. This CTP is non-stochastic, determined pre-treatment and has a unimodal distribution ranging from 0 to almost 100%. Notably, CTP is drug specific. We found that differential serine/threonine phosphorylation of the insulin receptor substrate 1 (IRS1) protein determines the CTP of lung and of head and neck cancer cells under epidermal growth factor receptor inhibition, both in vitro and in vivo. Indeed, the first-in-class IRS1 inhibitor NT219 was highly synergistic with anti-epidermal growth factor receptor therapy across multiple in vitro and in vivo models. Elucidation of drug-specific mechanisms that determine the degree and stability of cellular CTP may establish a framework for the elimination of cancer persisters, using new rationally designed drug combinations. Straussman and colleagues undertake clonal analyses and show that drug tolerance to EGFR therapy in lung cancer cell populations is an inherited continuous trait that is determined by IRS1 phosphorylation.

Profiling tumor bacteria Bacteria are well-known residents in human tumors, but whether their presence is advantageous to the tumors or to the bacteria themselves has been unclear. As an initial step toward addressing this question, Nejman et al. produced an exhaustive catalog of the bacteria present in more than 1500 human tumors representing seven different tumor types (see the Perspective by Atreya and Turnbaugh). They found that the bacteria within tumors were localized within both cancer cells and immune cells and that the bacterial composition varied according to tumor type. Certain biologically plausible associations were identified. For example, breast cancer subtypes characterized by increased oxidative stress were enriched in bacteria that produce mycothiol, which can detoxify reactive oxygen species. Science , this issue p. 973 ; see also p. 938

Purpose Sleep is essential for life, as well as having a major impact on quality of life. Not much attention has been given to this important factor in the care of lung cancer patients. Patients and Methods We retrospectively analyzed a cohort of 404 lung cancer patients treated in our institute between 2010 and 2018. Data about sleep quality, distress and pain were self-reported by questionnaires administered to patients at their first clinic visit to the Institute of Oncology. Sex, age, histology, stage, smoking and marital status were extracted from the patients’ charts. Uni- and multi-variate analyses were carried out to evaluate the correlation of these factors with survival. Results Most patients reported some level of distress and pain. Sleep abnormalities were reported by 58.7% of patients. Distress, pain and bad sleep were correlated with shorter survival in univariate analyses; however, only sleep remained associated with survival in multivariate analysis. Patients reporting bad sleep had a median survival of 16 months, compared to 27 months for patients reporting good sleep (hazard ratio 1.83, 95% C.I. 1.27–2.65). Frequent arousals at night were more tightly correlated with survival than difficulty falling asleep. Conclusion Sleep quality, as reported by lung cancer patients, is highly correlated with survival. Further studies are required to comprehend whether poor sleep quality is directly impacting survival or is a result of the cancer aggressiveness and patients’ conditions.

e21110 Background: Immune checkpoint inhibitor (ICI) therapy represents one of the most promising cancer treatments to date. However, despite unprecedented rates of durable response, only a small proportion of patients benefits from this approach. Major efforts are therefore required to characterize treatment resistance mechanisms, as well as to identify reliable biomarkers for response. We have previously shown that in response to various types of cancer therapy, including ICIs, the host may induce pro-tumorigenic processes that can promote therapy resistance. Here we examined systemic host-response proteomic profiles in non-small cell lung cancer (NSCLC) patients, aiming to discover biomarkers for response to ICI therapy and to unravel underlying resistance mechanisms. Methods: As part of our ongoing PROPHETIC clinical trial (NCT04056247), plasma samples were obtained at baseline (T0) and early-on treatment (T1; following the first treatment) from 120 NSCLC patients receiving ICI therapy. Proteomic profiling of the plasma samples was performed using proximity-extension assay (PEA) technology; validation was carried out for a fraction of the samples using ELISA-based arrays. To identify a proteomic signature that predicts clinical outcome, machine learning algorithms were applied following a random separation of the cohort into a discovery set and a validation set. Results: A proteomic signature predictive of response to treatment was identified and validated. Bioinformatic analysis identified potential mechanisms of resistance based on differentially expressed proteins associated with pro-tumorigenic biological processes. Statistical analysis of the clinical data identified multiple novel differential clinical parameters between responders and non-responders, either at baseline or by comparing T0 to T1, which may suggest host-mediated effects. Conclusions: Our study demonstrates the potential clinical utility of analyzing the host response to ICI therapy, in particular for the discovery of novel predictive biomarkers for NSCLC patient stratification. Clinical trial information: NCT04056247.

The most successful immunotherapeutic agents are blocking antibodies to either programmed cell death-1 (PD-1), an inhibitory receptor expressed on T lymphocytes, or to its ligand, programmed cell death-ligand 1 (PD-L1). Nevertheless, many patients do not respond, and additional approaches, specifically blocking other inhibitory receptors on T cells, are being explored. Importantly, the source of the ligands for these receptors are often the tumor cells. Indeed, cancer cells express high levels of PD-L1 upon stimulation with interferon-γ (IFN-γ), a major cytokine in the tumor microenvironment. The increase in PD-L1 expression serves as a negative feedback towards the immune system, and allows the tumor to evade the attack of immune cells. A potential novel immunoregulator is mesencephalic astrocyte-derived neurotrophic factor (MANF), an endoplasmic reticulum (ER)-resident protein that is secreted from pancreatic beta cells upon cytokines activation, and can induce an alternatively activated macrophage phenotype (M2), and thus may support tumor growth. While MANF was shown to be secreted from pancreatic beta cells, its IFN-γ-induced secretion from tumor cells has never been assessed. Here we found that IFN-γ induced MANF secretion from diverse tumor cell-lines—melanoma cells, colon carcinoma cells and hepatoma cells. Mechanistically, there was no increase in MANF RNA or intracellular protein levels upon IFN-γ stimulation. However, IFN-γ induced ER calcium depletion, which was necessary for MANF secretion, as Dantrolene, an inhibitor of ER calcium release, prevented its secretion. Thus, MANF is secreted from IFN-γ-stimulated tumor cells, and further studies are required to assess its potential as a drug target for cancer immunotherapy.

Objectives Non-small cell lung cancer (NSCLC) is the leading cause of cancer-related death world-wide. Immune checkpoint inhibitors (ICI) have become the most promising type of treatment in oncology in general, and significantly so in NSCLC. Limited data is available about mechanisms of primary resistance. Data is lacking about mechanisms involved in acquired resistance or mixed responses in NSCLC. We aimed to identify mechanisms of resistance by studying biopsies taken from sites of secondary progression. Materials and methods We identified all cases of NSCLC that have received ICI for advanced disease in our institute. Of these cases, those that have demonstrated acquired resistance or mixed responses, and have underwent a biopsy from a progressive lesion were analyzed. Selected specimens were subjected to next-generation sequencing (NGS; Oncomine™ Solid Tumour Fusion Transcript Kit). Results Out of 664 lung cancer cases, 249 were NSCLC that have received ICI. Of these, eight cases matched our search criteria. Two of them demonstrated transformation to small cell lung cancer (SCLC; 2/8, 25%). NGS verified a common origin to a matched pre-treatment NSCLC specimen and an on-treatment progressive SCLC specimen. In two cases no tumor cells were found and in the remaining four the pathology was similar to the initial biopsy. In one of the cases of SCLC transformation platinum-etoposide chemotherapy was administered, with short-term benefit only and further disease progression. Conclusion Mechanisms of acquired resistance to ICI include SCLC transformation. Repeat biopsies of progressing lesions after initial response or in cases of mixed response can shed light on mechanisms of resistance.

8534 Background: Resected NSCLC clinical stage I or II harbor a 5 year survival of only 30-50%. Immunotherapy might be more effective in low-burden disease. We hypothesized that neo-adjuvant immunotherapy is a feasible, safe and effective treatment (Tx) for early stage NSCLC. Methods: MK3475-223 is an ongoing phase I study of neoadjuvant pembrolizumab in stage I-II NSCLC. All Pembro Txs are 200mg q 3 weeks (wks). Objectives: determine safety; recommended phase 2 dose/schedule; pathological & radiological response. Doses-schedule limiting toxicities (DLT) were defined as significant surgical complications (bleeding, delayed wound healing, ARDS, prolonged air-leak) or a significant delay of surgery. The doses-schedule escalation cohorts were (i) single pembro dose 3 wk prior to surgery; (ii) 2 pembro doses, 2 wks later surgery; (iii) 2 pembro doses, 1 wk later surgery. Expansion cohort received the doses-schedule of cohort (iii). Percentages of remaining viable tumor in the post-Tx were assessed, 10% or less was considered amajor pathological response (MPR). IHC for pre-Tx PDL1 was done. Efficacy was evaluated for the patients who had received 2 doses of pembrolizumab. Results: No DLT occurred in the dose-schedule escalation cohorts. 10 patients received 2 cycles of neo-adjuvant pembrolizumab. 4 patients achieved a MPR (4/10 who received 2 cycles of pembro; 40%; 95% C.I. 16.7-68.8%). No correlation is seen between the levels of PDL1 pre-Tx and the pathologic response. Size of the tumor and N status was also not in any apparent correlation with MPR (data not shown). Interestingly, all of the MPR cases had a relatively long interval from 1st Tx till surgery. Clinical trial information: NCT02938624. Conclusions: Neo-adjuvant pembro is safe and feasible. A promising sign of efficacy is seen. Achieving MPR might require a longer 1st-Tx-surgery interval. Predictive biomarkers for response might be different from those in advanced disease. Recruitment and correlative studies are ongoing.[Table: see text]

Background Non–small-cell lung cancer (NSCLC) includes 2 major histologic subtypes: squamous cell carcinoma and non-squamous carcinoma, mainly adenocarcinoma, a distinction that carries significant clinical and therapeutic implications. NSCLC is diagnosed as adenocarcinoma or as squamous cell carcinoma on the basis of histologic parameters. However, when morphology is inconclusive, tumors with immunohistochemistry (IHC) findings characteristic of adenocarcinoma are referred to as “NSCLC favor adenocarcinoma” (NFA). Our aim was to evaluate whether pulmonary adenocarcinoma diagnosis on the basis of morphology had a similar prognosis compared with NFA. Patients and Methods Patients with advanced NSCLC non-squamous carcinoma who were treated with a platinum-pemetrexed doublet as first-line combination chemotherapy were identified. Demographic, clinical, laboratory, and pathological data including the method of pathological diagnosis (morphology or IHC) was extracted from the clinical charts. The correlation between the various parameters and overall survival was evaluated. Results Lack of adenocarcinoma morphology, male sex, smoking history, and negative thyroid transcription factor 1 IHC were associated with worse prognosis and shorter overall survival in multivariate analysis. High white blood cell count, absolute neutrophil count, neutrophil to lymphocyte ratio, and low albumin levels were associated with shorter overall survival only in univariate analysis. Conclusion Pulmonary adenocarcinoma has a better prognosis than NFA, regarding advanced NSCLC treated with platinum-pemetrexed combination chemotherapy. This distinction should be a stratification factor in clinical trials and a prognostic factor to consider in analysis of previous trials.

p53 deficiency enhances the efficiency of somatic cell reprogramming to a pluripotent state. As p53 is usually mutated in human tumors and many mutated forms of p53 gain novel activities, we studied the influence of mutant p53 (mut-p53) on somatic cell reprogramming. Our data indicate a novel gain of function (GOF) property for mut-p53, which markedly enhanced the efficiency of the reprogramming process compared with p53 deficiency. Importantly, this novel activity of mut-p53 induced alterations in the characteristics of the reprogrammed cells. Although p53 knockout (KO) cells reprogrammed with only Oct4 and Sox2 maintained their pluripotent capacity in vivo, reprogrammed cells expressing mutant p53 lost this capability and gave rise to malignant tumors. This novel GOF of mut-p53 is not attributed to its effect on proliferation, as both p53 KO and mut-p53 cells displayed similar proliferation rates. In addition, we demonstrate an oncogenic activity of Klf4, as its overexpression in either p53 KO or mut-p53 cells induced aggressive tumors. Overall, our data show that reprogrammed cells with the capacity to differentiate into the three germ layers in vitro can form malignant tumors, suggesting that in genetically unstable cells, such as those in which p53 is mutated, reprogramming may result in the generation of cells with malignant tumor-forming potential.

e21230Background: Resistance to immune checkpoint inhibitors (ICPi) is common, either primary, or as acquired resistance after an initial response. Mechanisms of resistance are poorly documented. M...

The prostate is composed of a number of different cell populations. The interaction between them is crucial for the development and proper function of the prostate. However, the effect of the molecular cross talk between these cells in the course of carcinogenesis is still unclear. Employing an approach wherein immortalized epithelial cells and immortalized human fibroblasts were cocultured, we show that normal associated fibroblasts (NAF) and cancer-associated fibroblasts (CAF) differentially influenced the growth and proliferation of immortalized human prostate epithelial cells. Whereas NAFs inhibited the growth of immortalized epithelial cells but promoted the growth of metastatic PC-3 cells, CAFs promoted the growth of immortalized epithelial cells but not of PC-3. Cytokine arrays revealed that NAFs secreted higher levels of tumor necrosis factor-α compared with CAFs whereas CAFs secreted higher levels of interleukin-6 (IL-6) compared with NAFs. The growth-inhibiting effects of NAFs were counteracted by the addition of IL-6, and the growth-promoting effects exerted by the CAFs were counteracted by tumor necrosis factor-α. Furthermore, CAFs induced the migration of endothelial cells in an IL-6–dependent manner. Here, we show that normal fibroblast cells have a protective function at very early stages of carcinogenesis by preventing immortalized epithelial cells from proliferating and forming new blood vessels whereas CAFs aid immortalized epithelial cells to further develop. (Mol Cancer Res 2009;7(8):1212–23)

SummaryThe “BH3-only” proapoptotic BCL-2 family members are sentinels of intracellular damage. Here, we demonstrated that the BH3-only BID protein partially localizes to the nucleus in healthy cells, is important for apoptosis induced by DNA damage, and is phosphorylated following induction of double-strand breaks in DNA. We also found that BID phosphorylation is mediated by the ATM kinase and occurs in mouse BID on two ATM consensus sites. Interestingly, BID−/− cells failed to accumulate in the S phase of the cell cycle following treatment with the topoisomerase II poison etoposide; reintroducing wild-type BID restored accumulation. In contrast, introducing a nonphosphorylatable BID mutant did not restore accumulation in the S phase and resulted in an increase in cellular sensitivity to etoposide-induced apoptosis. These results implicate BID as an ATM effector and raise the possibility that proapoptotic BID may also play a prosurvival role important for S phase arrest.

Introduction Breast cancer progression is promoted by stromal cells that populate the tumors, including cancer-associated fibroblasts (CAFs) and mesenchymal stem/stromal cells (MSCs). The activities of CAFs and MSCs in breast cancer are integrated within an intimate inflammatory tumor microenvironment (TME) that includes high levels of tumor necrosis factor α (TNF-α) and interleukin 1β (IL-1β). Here, we identified the impact of TNF-α and IL-1β on the inflammatory phenotype of CAFs and MSCs by determining the expression of inflammatory chemokines that are well-characterized as pro-tumorigenic in breast cancer: CCL2 (MCP-1), CXCL8 (IL-8) and CCL5 (RANTES). Methods Chemokine expression was determined in breast cancer patient-derived CAFs by ELISA and in patient biopsies by immunohistochemistry. Chemokine levels were determined by ELISA in (1) human bone marrow-derived MSCs stimulated by tumor conditioned media (Tumor CM) of breast tumor cells (MDA-MB-231 and MCF-7) at the end of MSC-to-CAF-conversion process; (2) Tumor CM-derived CAFs, patient CAFs and MSCs stimulated by TNF-α (and IL-1β). The roles of AP-1 and NF-κB in chemokine secretion were analyzed by Western blotting and by siRNAs to c-Jun and p65, respectively. Migration of monocytic cells was determined in modified Boyden chambers. Results TNF-α (and IL-1β) induced the release of CCL2, CXCL8 and CCL5 by MSCs and CAFs generated by prolonged stimulation of MSCs with Tumor CM of MDA-MB-231 and MCF-7 cells. Patient-derived CAFs expressed CCL2 and CXCL8, and secreted CCL5 following TNF-α (and IL-1β) stimulation. CCL2 was expressed in CAFs residing in proximity to breast tumor cells in biopsies of patients diagnosed with invasive ductal carcinoma. CCL2 release by TNF-α-stimulated MSCs was mediated by TNF-RI and TNF-RII, through the NF-κB but not via the AP-1 pathway. Exposure of MSCs to TNF-α led to potent CCL2-induced migration of monocytic cells, a process that may yield pro-cancerous myeloid infiltrates in breast tumors. Conclusions Our novel results emphasize the important roles of inflammation-stroma interactions in breast cancer, and suggest that NF-κB may be a potential target for inhibition in tumor-adjacent stromal cells, enabling improved tumor control in inflammation-driven malignancies. Electronic supplementary material The online version of this article (doi:10.1186/s13287-015-0080-7) contains supplementary material, which is available to authorized users.

Mutations in the p53 tumor suppressor protein are highly frequent in tumors and often endow cells with tumorigenic capacities. We sought to examine a possible role for mutant p53 in the cross-talk between cancer cells and their surrounding stroma, which is a crucial factor affecting tumor outcome. Here we present a novel model which enables individual monitoring of the response of cancer cells and stromal cells (fibroblasts) to co-culturing. We found that fibroblasts elicit the interferon beta (IFNβ) pathway when in contact with cancer cells, thereby inhibiting their migration. Mutant p53 in the tumor was able to alleviate this response via SOCS1 mediated inhibition of STAT1 phosphorylation. IFNβ on the other hand, reduced mutant p53 RNA levels by restricting its RNA stabilizer, WIG1. These data underscore mutant p53 oncogenic properties in the context of the tumor microenvironment and suggest that mutant p53 positive cancer patients might benefit from IFNβ treatment.

PD1-PDL1 interaction is one mechanism of tumor evasion of the immune system, and inhibitors of this interaction can allow cancer cell killing by cytotoxic T cells. In NSCLC as well as in most other cancers, the clinical benefit from such inhibitors is far from universal; around 20% of tumors respond to this treatment. Response of tumors to anti-cancer agents depends on interactions of epithelial tumor cells and the microenvironment, including stromal cells such as fibroblasts, immune cells and extracellular matrix. Studying cell signaling and drug-sensitivity of cancer should take into consideration the different compartments of an individual tumor. Regarding immunotherapy, manipulating regulators of PDL1 expression might augment the activity of these drugs, or possibly be active as an immunotherapy on its own. Specifically, little is known about the impact of chemotherapy, radiotherapy or targeted agents on the expression and activity of the PD1-PDL1 signaling in human cancer. Combining such treatments with immunotherapy is a potentially promising approach that is currently investigated clinically. However, the number of potential combinations is vast, and no valid and convenient experimental model exists to test candidate treatments and combinations. Experimental procedures: Ex vivo organ cultures (EVOC) were directly established from fresh NSCLC tissues, as a model that recapitulates real tumor and its microenvironment, including immune cells. Tissue elements were mechanistically dispersed to cell clumps (30-100 cells per clump), or cut to one cubic mm pieces and placed in culture. LDH release was used as a surrogate of cell death. Samples were analyzed by formalin fixation and paraffin embedment, sectioning and hematoxilin and eosin visualization of cells. PDL1 mRNA and protein levels were measured by RT-PCR and western blots. Results: Cell viability of NSCLC EVOC is maintained over a time window of at least 4-7 days. Cytotoxic drugs evoke cell death. PDL1 mRNA and protein levels are elevated in NSCLC EVOC in response to inflammation signals as Interferon gamma. Glucocorticoid steroidal drugs causes reduction in PDL1 mRNA and protein in NSCLC EVOC. Cisplatin treatment causes elevation in PDL1 protein. Variability in basal and induced PDL1 protein levels was detected in response to inflammation signals in EVOCs generated from different patients. Conclusions: Our results indicate the feasibility of EVOC for NSCLC and the potential to use it as a model to study the impact of immunotherapy agents, alone or in combination with other therapeutic tools such as chemotherapy or radiotherapy. Citation Format: Jair Bar, Inbal Daniel-Meshulam, Amir Onn, Alon Ben-Nun, David Simansky, Nona Zeitlin, Nir Golan, Meirav Rokah, Ronni Ben-Avi, Iris Kamer. Modeling immunotherapy in ex vivo organ culture of non-small cell lung cancer (NSCLC). [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 4910.

International audience; A mutation within one allele of the p53 tumor suppressor gene can inactivate the remaining wild-type allele in a dominant-negative manner and in some cases can exert an additional oncogenic activity, known as mutant p53 'gain of function' (GOF). To study the role of p53 mutations in prostate cancer and to discriminate between the dominant-negative effect and the GOF activity of mutant p53, we measured, using microarrays, the expression profiles of three immortalized prostate epithelial cultures expressing wild-type, inactivated p53 or mutated p53. Analysis of these gene expression profiles showed that both inactivated p53 and p53(R175H) mutant expression resulted in the upregulation of cell cycle progression genes. A second group, which was upregulated exclusively by mutant p53(R175H), was predominantly enriched in developmental genes. This group of genes included the Twist1, a regulator of metastasis and epithelial-mesenchymal transition (EMT). Twist1 levels were also elevated in metastatic prostate cancer-derived cell line DU145, in immortalized lung fibroblasts and in a subset of lung cancer samples, all in a mutant p53-dependent manner. p53(R175H) mutant bearing immortalized epithelial cells showed typical features of EMT, such as higher expression of mesenchymal markers, lower expression of epithelial markers and enhanced invasive properties in vitro. The mechanism by which p53(R175H) mutant induces Twist1 expression involves alleviation of the epigenetic repression. Our data suggest that Twist1 expression might be upregulated following p53 mutation in cancer cells.

Prostate cancer is the most common non-dermatologic malignancy in men in the Western world. Recently, a frequent chromosomal aberration fusing androgen regulated TMPRSS2 promoter and the ERG gene (TMPRSS2/ERG) was discovered in prostate cancer. Several studies demonstrated cooperation between TMPRSS2/ERG and other defective pathways in cancer progression. However, the unveiling of more specific pathways in which TMPRSS2/ERG takes part, requires further investigation. Using immortalized prostate epithelial cells we were able to show that TMPRSS2/ERG over-expressing cells undergo an Epithelial to Mesenchymal Transition (EMT), manifested by acquisition of mesenchymal morphology and markers as well as migration and invasion capabilities. These findings were corroborated in vivo, where the control cells gave rise to discrete nodules while the TMPRSS2/ERG-expressing cells formed malignant tumors, which expressed EMT markers. To further investigate the general transcription scheme induced by TMPRSS2/ERG, cells were subjected to a microarray analysis that revealed a distinct EMT expression program, including up-regulation of the EMT facilitators, ZEB1 and ZEB2, and down-regulation of the epithelial marker CDH1(E-Cadherin). A chromatin immunoprecipitation assay revealed direct binding of TMPRSS2/ERG to the promoter of ZEB1 but not ZEB2. However, TMPRSS2/ERG was able to bind the promoters of the ZEB2 modulators, IL1R2 and SPINT1. This set of experiments further illuminates the mechanism by which the TMPRSS2/ERG fusion affects prostate cancer progression and might assist in targeting TMPRSS2/ERG and its downstream targets in future drug design efforts.

cDNA microarray hybridization was used in an attempt to identify novel genes participating in cellular responses to prolonged hypoxia. One of the identified novel genes, designated Hi95 shared significant homology to a p53-regulated GADD family member PA26. In addition to its induction in response to prolonged hypoxia, the increased Hi95 transcription was observed following DNA damage or oxidative stress, but not following hyperthermia or serum starvation. Whereas induction of Hi95 by prolonged hypoxia or by oxidative stress is most likely p53-independent, its induction in response to DNA damaging treatments (gamma- or UV-irradiation, or doxorubicin) occurs in a p53-dependent manner. Overexpression of Hi95 full-length cDNA was found toxic for many types of cultured cells directly leading either to their apoptotic death or to sensitization to serum starvation and DNA damaging treatments. Unexpectedly, conditional overexpression of the Hi95 cDNA in MCF7-tet-off cells resulted in their protection against cell death induced by hypoxia/glucose deprivation or H(2)O(2). Thus, Hi95 gene seems to be involved in complex regulation of cell viability in response to different stress conditions.

Hypoxia is an important factor that elicits numerous physiological and pathological responses. One of the major gene expression programs triggered by hypoxia is mediated through hypoxia-responsive transcription factor hypoxia-inducible factor 1 (HIF-1). Here, we report the identification and cloning of a novel HIF-1-responsive gene, designated RTP801. Its strong up-regulation by hypoxia was detected both in vitro and in vivo in an animal model of ischemic stroke. When induced from a tetracycline-repressible promoter, RTP801 protected MCF7 and PC12 cells from hypoxia in glucose-free medium and from H(2)O(2)-triggered apoptosis via a dramatic reduction in the generation of reactive oxygen species. However, expression of RTP801 appeared toxic for nondividing neuron-like PC12 cells and increased their sensitivity to ischemic injury and oxidative stress. Liposomal delivery of RTP801 cDNA to mouse lungs also resulted in massive cell death. Thus, the biological effect of RTP801 overexpression depends on the cell context and may be either protecting or detrimental for cells under conditions of oxidative or ischemic stresses. Altogether, the data suggest a complex type of involvement of RTP801 in the pathogenesis of ischemic diseases.

Introduction: Insight into the processes of tumor initiation and progression as well as metastatic spread and response to therapies requires studies that take into consideration the stromal and epithelial components of tumors. Both FoxM1 and p53 have a major role in the progression, metastasis and chemo-resistance of non-small cell lung cancer (NSCLC). p53 is a well-recognized tumor-suppressor gene, commonly mutated in NSCLC and correlated with tumor aggressiveness. An anti-tumor role of p53 in the stroma has been demonstrated by us and others. p53 is reported to suppress FoxM1 transcription. FoxM1 is an oncogene, contributing to lung cancer progression and metastatic spread. Little is known about the role of FoxM1 in cancer's micro-environment. We hypothesized that tumor-induced-downregulation of p53 and upregulation of FoxM1 in the stromal compartments promotes lung cancer progression, metastatic spread and chemo-resistance. Materials and Methods: Cancer associated fibroblasts (CAFs) and normal fibroblasts (NFs) were produced from fresh lung tumor specimens. Cell lines and primary cells were grown in standard tissue culture conditions. Co-cultures were performed using transwell culture systems. DNA damage was induced by cisplatin treatment. Expression levels of mRNA and proteins were tested by real-time RT-PCR and western blots. Results: We have found FoxM1 levels to be higher in primary lung CAFs compared to NFs. In addition, CAFs that were treated with conditioned media of transformed epithelial cells showed down-regulation of stromal-p53 and up-regulation of FoxM1, in DNA damage conditions. mRNA levels of FoxM1 remain stable. While cancer-cells-CM up-regulate FoxM1 in CAFs, it was found to down-regulates it in NFs, suggesting both cancer and CAFs have evolved a unique mechanism of FoxM1 induction in stroma. In order to examine a possible paracrine effect between p53 levels in the stroma, and FoxM1 levels in tumor cells, we co-cultivated fibroblasts knocked-down for p53 with lung cancer cells and found up-regulation of FoxM1 the tumor cells. Summary: We demonstrate up-regulation of stromal FoxM1 by cancer-secreted-factors as well as by stable CAFs modifications, concomitantly to stromal p53 down-regulation. High stromal FoxM1 may promote tumor cells aggressiveness, similarly to low stromal p53, possibly being downstream to p53. Elaboration of these pathways will deepen our understanding of lung cancer and suggest novel therapeutic targets. Citation Format: Iris Kamer, Inbal Daniel, Gili Perry, Amir Onn, Jair Bar. Stromal FoxM1 and p53 in lung cancer as mediators of tumor progression, metastatic spread and chemo-resistance. [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 1153. doi:10.1158/1538-7445.AM2014-1153

Background: NSCLC is the most common cause of cancer-related death. Platinum-based chemotherapy is the mainstay of treatment, but a variety of mechanisms lead to platinum-resistance. ATF3 is a transcription factor, activated in response to a wide variety of stress signals including DNA damage and hypoxia. We recently demonstrated a role for ATF3 as an important regulator of platinum-induced cytotoxicity. In this study, we hypothesize that ATF3 expression correlates with platinum-sensitivity/resistance in NSCLC. Methods: ATF3 induction was examined by Western blots and real-time RT-PCR in isogenic sets of platinum- sensitive (S) or induced resistant (R) NSCLC cell lines. A 1200 compound library was screened to identify platinum-sensitizers in both sets of cell lines. Complete RNA sequencing (RNA-seq) was performed in parental (S) and resistant (R) derived cell lines comparing expression patterns of either untreated or platinum treated cells. Similarly, platinum R and S tumors were identified by screening NSCLC patients’ clinical records and expression patterns compared with RNA-seq analysis. Results: Both mRNA and potein levels of ATF3 were induced 35-120 fold (mRNA) by cisplatin treatment in S cell lines, but only 1-12 fold (mRNA) in the corresponding R lines. The 1200 compound library screen of FDA approved compounds identified several commonly used chemotherapeutic agents as sensitizers of platinum cytotoxicity, as well as vorinostat, a histone deacetylase inhibitor that sensitized only S but not R cell lines. An analogue of this agent, M344, enhanced ATF3 induction and cisplatin cytotoxicity in the S lines but not in the R lines. Comparing RNA-seq results of the S and R lines revealed up-regulation of GADD45A, ATF3 and DDIT3/CHOP in the S but not R cell lines. Comparing samples of S and R NSCLC tumors by RNA-seq demonstrated ATF3 to be among the five genes significantly up-regulated in the S tumors compared to the R tumors. Conclusions: Stress-induced ATF3 is correlated with platinum-sensitivity in NSCLC cells. Tumor ATF3 levels represent a potential predictive marker of response to platinum-based treatment in NSCLC. Revealing the mechanism of ATF3 induction by platinum may lead to the identification of novel platinum-sensitizing therapeutic targets. Citation Format: Jair Bar, Ivan Gorn-Hondermann, Reid Stephanie, Patricia Moretto, Iris Shiran, Shlomit Jessel, Marina Perelman, Eyal Heller, Iris Kamer, Inbal Daniel-Meshulam, Glenwood D. Goss, Jim Dimitroulakos. Activating transcription factor 3 (ATF3) down-regulation correlates with platinum resistance in non-small cell lung cancer (NSCLC). [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 895. doi:10.1158/1538-7445.AM2013-895