Null Lung Research Articles

Abstract 1791: Metabolic rewiring promotes metastatic potential upon glutamine deprivation in STK11 null KRAS-driven lung adenocarcinoma

Abstract Lung adenocarcinoma (LUAD) with concurrent oncogenic KRAS and STK11 loss-of-function mutations define an aggressive subtype characterized, in part, by increased metastasis. Loss of STK11, a tumor suppressor and nutrient sensor, leads to dysregulation of many critical cellular processes, including metabolism. As such, STK11 null cancers are “glutamine addicted” to support proliferative properties and the tumor microenvironment therefore becomes glutamine depleted. We hypothesize that conditions of glutamine stress promote metastatic potential in STK11 null KRAS-driven LUAD due to metabolic rewiring. To test this hypothesis, we utilized a cell culture model of KRAS-driven LUAD cell lines and corresponding STK11 knockout cell lines (∆STK11). Parental and ∆STK11 cells underwent the Seahorse mitochondrial stress test in full and glutamine-deficient media to obtain parameters of mitochondrial respiration at baseline and under conditions reflective of the tumor microenvironment, respectively. At baseline, ∆STK11 cells had a hypermetabolic phenotype associated with enhanced glutamine utilization. Deprivation of glutamine resulted in decreased mitochondrial respiration along with a significant increase in live, detached ∆STK11 cells compared to the parental line. Upon further examination, the detached ∆STK11 cells maintained the ability to re-adhere and proliferate in full media while the detached parental cells did not. Additionally, expression of pro-survival, anti-apoptotic and EMT markers in ∆STK11 cells were increased upon glutamine deprivation. To determine the mechanism(s) underlying this pro-metastatic phenotype, we employed heavy nitrogen labeling which revealed an upregulation of the hexosamine biosynthetic pathway (HBP). The HBP is an offshoot of glycolysis that serves as a central hub to regulate many cancer fitness pathways via O-GlcNAcylation; the addition of a GlcNAc moiety to serine/threonine residues of target proteins. Further assessment of O-GlcNAcylation levels via western and far western blot analysis revealed that parental cells had decreasing HBP flux concordant with decreasing glutamine concentration while ∆STK11 cells, conversely, had enhanced HBP flux upon decreasing glutamine availability. These observations suggest ∆STK11 cells utilize the HBP as a protective shunt under decreased glutamine availability. We are currently characterizing the invasive potential and anchorage-independence of parental and ∆STK11 LUAD cells upon glutamine deprivation. Future studies aim to establish the impact of HBP perturbation, both genetically and pharmacologically, on the described measures of metastatic potential. Overall, this work reveals novel insight into the molecular mechanisms altered downstream of STK11 loss that link glutamine metabolism with metastatic properties in KRAS-driven LUAD. Citation Format: Shannon Prior, Logan Sands, Sean Lenahan, Hailey Sarausky, Melissa Scheiber, David Seward, Paula Deming. Metabolic rewiring promotes metastatic potential upon glutamine deprivation in STK11 null KRAS-driven lung adenocarcinoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 1791.

Understanding the Role of Flavonoid Based Small Molecules in Modulating the Oncogenic Protein-Protein Interactions: A Quest for Therapeutic Arsenal

We explored the anticancer activity of two synthetic flavonoid-based small molecules, HMDC and HMDF, with bioactive methylenedioxy functionality. HMDF inhibited the proliferation of the p53 wild-type (NCIH460 and A549), and p53 null (NCIH1299) non-small cell lung cancer and breast cancer (MCF-7) cells more potently than HMDC without significant cytotoxic effects on the normal lung-epithelial (L132) and macrophage (Raw 264.7) cells. HMDF mediated reduction of the cell proliferation occurred due to its attachment at the p53-binding domain of MDM2 (also evident from molecular docking analysis), which induced the disruption of the p53-MDM2 interactions. Ultimately, a higher expression of p53 in the NCIH460 cells was observed. The up-regulated p53 level instigated apoptosis of cancer cells. However, MDM2 expression level remained unaltered. The docking studies further indicate that HMDF can suppress the anti-apoptotic activity of Bcl-2 protein by blocking its BH3 domain.

Lung Tumor Cell-Derived Exosomes Promote M2 Macrophage Polarization.

Cellular cross-talk within the tumor microenvironment (TME) by exosomes is known to promote tumor progression. Tumor promoting macrophages with an M2 phenotype are suppressors of anti-tumor immunity. However, the impact of tumor-derived exosomes in modulating macrophage polarization in the lung TME is largely unknown. Herein, we investigated if lung tumor-derived exosomes alter transcriptional and bioenergetic signatures of M0 macrophages and polarize them to an M2 phenotype. The concentration of exosomes produced by p53 null H358 lung tumor cells was significantly reduced compared to A549 (p53 wild-type) lung tumor cells, consistent with p53-mediated regulation of exosome production. In co-culture studies, M0 macrophages internalized tumor-derived exosomes, and differentiated into M2 phenotype. Importantly, we demonstrate that tumor-derived exosomes enhance the oxygen consumption rate of macrophages, altering their bioenergetic state consistent with that of M2 macrophages. In vitro co-cultures of M0 macrophages with H358 exosomes demonstrated that exosome-induced M2 polarization may be p53 independent. Murine bone marrow cells and bone marrow-derived myeloid-derived suppressor cells (MDSCs) co-cultured with lewis lung carcinoma (LLC)-derived exosomes differentiated to M2 macrophages. Collectively, these studies provide evidence for a novel role for lung tumor-exosomes in M2 macrophage polarization, which then offers new therapeutic targets for immunotherapy of lung cancer.

An updated meta-analysis of the relationship between glutathione S-transferase T1 null/presence gene polymorphism and the risk of lung cancer.

There were many reports published on the relationship between glutathione S-transferase T1 (GSTT1) null/presence gene polymorphism and the risk of lung cancer in these years. In previous, we conducted a meta-analysis to evaluate the relationship between GSTT1 null/presence gene polymorphism and the risk of lung cancer. This study was conducted to update it. The association studies were identified from PubMed and Cochrane Library on March 1, 2016. Sixty-three reports were recruited into this meta-analysis for the association of null genotype of GSTT1 with lung cancer susceptibility, consisting of 21,220 patients with lung cancer and 21,496 controls. There was a marked association between GSTT1 null genotype and lung cancer risk in overall populations and in Asians (overall populations: Odds ratio [OR] = 1.17, 95% confidence interval [95% CI]: 1.07-1.28, P = 0.006; Asians: OR = 1.41, 95% CI: 1.23-1.62, P < 0.00001). However, GSTT1 null genotype was not associated with the risk of lung cancer in Caucasians, Brazilian population, and Africans. GSTT1 null genotype is associated with the lung cancer risk in overall populations and in Asians.

Metabolomic Analysis Reveals Unique Biochemical Signatures Associated with Protection from Radiation Induced Lung Injury by Lack of cd47 Receptor Gene Expression.

The goal of this study was to interrogate biochemical profiles manifested in mouse lung tissue originating from wild type (WT) and cd47 null mice with the aim of revealing the in vivo role of CD47 in the metabolic response to ionizing radiation, especially changes related to the known association of CD47 deficiency with increased tissue viability and survival. For this objective, we performed global metabolomic analysis in mouse lung tissue collected from (C57Bl/6 background) WT and cd47 null mice with and without exposure to 7.6 Gy whole body radiation. Principal component analysis and hierarchical clustering revealed a consistent separation between genotypes following radiation exposure. Random forest analysis also revealed a unique biochemical signature in WT and cd47 null mice following treatment. Our data show that cd47 null irradiated lung tissue activates a unique set of metabolic pathways that facilitate the handling of reactive oxygen species, lipid metabolism, nucleotide metabolism and nutrient metabolites which may be regulated by microbial processing. Given that cd47 has pleiotropic effects on responses to ionizing radiation, we not only propose this receptor as a therapeutic target but postulate that the biomarkers regulated in this study associated with radioprotection are potential mitigators of radiation-associated pathologies, including the onset of pulmonary disease.

Autophagy Regulated by Gain of Function Mutant p53 Enhances Proteasomal Inhibitor-Mediated Cell Death through Induction of ROS and ERK in Lung Cancer Cells.

Mutations in p53, especially gain of function (GOF) mutations, are highly frequent in lung cancers and are known to facilitate tumor aggressiveness. Yet, the links between mutant GOF-p53 and lung cancers are not well established. In the present study, we set to examine how we can better sensitize resistant GOF-p53 lung cancer cells through modulation of cellular protein degradation machineries, proteasome and autophagy. H1299 p53 null lung cancer cells were stably transfected with R273H mutant GOF-p53 or wild-type (wt) p53 or empty vectors. The presence of R273H-P53 conferred the cancer cells with drug resistance not only against the widely used chemotherapeutic agents like cisplatin (CDDP) or 5-flurouracil (5-FU) but also against potent alternative modes of therapy like proteasomal inhibition. Therefore, there is an urgent need for new strategies that can overcome GOF-p53 induced drug resistance and prolong patient survival following failure of standard therapies. We observed that the proteasomal inhibitor, peptide aldehyde N-acetyl-leu-leu-norleucinal (commonly termed as ALLN), caused an activation of cellular homeostatic machinery, autophagy in R273H-P53 cells. Interestingly, inhibition of autophagy by chloroquine (CQ) alone or in combination with ALLN failed to induce enhanced cell death in the R273H-P53 cells; however, in contrast, an activation of autophagy by serum starvation or rapamycin increased sensitivity of cells to ALLN-induced cytotoxicity. An activated autophagy was associated with increased ROS and ERK signaling and an inhibition of either ROS or ERK signaling resulted in reduced cytotoxicity. Furthermore, inhibition of GOF-p53 was found to enhance autophagy resulting in increased cell death. Our findings provide novel insights pertaining to mechanisms by which a GOF-p53 harboring lung cancer cell is better sensitized, which can lead to the development of advanced therapy against resistant lung cancer cells.

Abstract 1323: A p53-dependent switch between cytoprotective and nonprotective autophagy influences tumor cell sensitivity to cisplatin

Abstract Autophagy is a multi-step, homeostatic process through which cells turnover dysfunctional organelles and proteins. Previous work in our laboratory has identified multiple functional roles of autophagy, specifically cytoprotective, cytotoxic, cytostatic and nonprotective, when subjected to radiation and chemotherapy. Furthermore, we have reported on the existence of an autophagic switch between one functional form (generally cytoprotective) to the other forms. To further explore the autophagic switch, we utilized p53 wild type (p53 +/+) and p53 null (p53 -/-) H460 non-small cell lung cancer (NSCLC) cell lines exposed to cisplatin. The extent of autophagy was similar in both cell lines, but the rate and extent of apoptosis was higher in the p53 +/+ cells, which showed greater cisplatin sensitivity. Pharmacological (chloroquine, 3-Methyladenine) and genetic (ATG5 silencing) inhibition of autophagy failed to sensitize the p53 +/+ H460 cells to cisplatin, suggesting that autophagy has a nonprotective role. In contrast, autophagy inhibition (CQ, 3-MA, or shATG5) increased sensitivity to cisplatin in the p53 -/- H460 cells, indicative of a cytoprotective function of autophagy. These studies support the premise that cytoprotective autophagy may confer resistance to cisplatin. Moreover, we confirm the pivotal role of p53 in determining the function of autophagy induced by cisplatin. Finally, we provide an additional example of a switch between the nonprotective and protective forms of autophagy in p53 wild type and p53 null H460 non-small cell lung cancer (NSCLC) cells, respectively. Citation Format: Jingwen Xu, Tareq Saleh, Nipa Patel, Yingliang Wu, Santiago Lima, David Gewirtz. A p53-dependent switch between cytoprotective and nonprotective autophagy influences tumor cell sensitivity to cisplatin [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 1323.

Nrf-2 transcriptionally activates P21Cip/WAF1 and promotes A549 cell survival against oxidative stress induced by H2O2.

Cancer cells possess elevated ROS coupled with increased levels of antioxidant enzymes which render them resistant against cytotoxic chemotherapies. Therefore, an understanding of the interaction between key molecules involved in stress adaptive mechanisms is important to innovate strategies against cancer cell chemoresistance. Here, the lung adenocarcinoma cell line A549 with constitutively expressed Nrf2 was found to be more tolerant to H2O2 (0.1, 0.2, 0.5 and 1 mM) than normal lung cell line L132 or p53 null lung cancer cell line H1299. Maximum cytoprotection was observed at 0.2 mM H2O2 accompanied by a significant increase in p21, Nrf2 and antioxidant enzymes in A549 cells. The increased p21 expression was independent of p53 but dependent on Nrf2 as evident from qPCR, Western blotting and dual luciferase assays after silencing Nrf-2 and p53 genes. Highly conserved Nrf-2 binding sites were identified in p21 promoter by bioinformatics and homology modeling which was further confirmed by ChIP and reporter assay.

C-terminal region of human p53 attenuates buffalo p53N-terminal-specific transactivation of p21 promoter by modulating tetramerization of the protein.

Here, we have studied in p53 null H1299 lung carcinoma cells, the dominant-negative effect of human p53 (h-p53) on buffalo p53 (b-p53) induced nuclear transactivation-dependent function. Recently, we have isolated and cloned the full-length cDNA of buffalo p53. Buffalo and human p53 proteins exhibit a high degree of structural and functional similarities. In transiently transfected H1299 cell line b-p53 appeared to be more sensitive to Mdm2-mediated degradation as compared to h-p53, although its ability to transactivate p21 promoter was stronger than that ofthe human counterpart. This higher transactivation ability of b-p53 was lost in the presence of h-p53 suggesting, a dominant-negative effect of h-p53 on b-p53's transactivation of p21 promoter. Both human and buffalo p53 proteins could hetero-oligomerize but the b-p53 could tetramerize much faster than the h-p53. A chimeric cDNA construct of human p53 was made where the 1-260bpN-terminus was replaced with buffalo p53 counterpart and expressed in H1299 cell line. The tetramerization ability of the chimeric p53 protein was comparable to that of h-p53. Properties of b-p53 like stronger p21 transactivation and super sensitivity to Mdm2 mediated degradation were lacking in the chimeric protein. Thus, it is suggested that faster ability of tetramerization as well as higher transactivation property of buffalo p53 is determined by the interplay of N- and C-terminal domains through macromolecular interactions.

Combined effects of glutathione S-transferase M1 and T1 polymorphisms on risk of lung cancer: Evidence from a meta-analysis.

Many studies have reported an association between the glutathione S-transferase M1 null and T1 null polymorphisms and lung cancer risk. However, the combined effects of GSTM1 null and GSTT1 null polymorphisms have not been reported previously. We, therefore, performed a meta-analysis to investigate the combined effects. 40 publications with 44 case–control studies were selected in the meta-analysis, including 13,706 cases and 13,093 controls. Significant association was observed between the combined effects of GSTM1 and GSTT1 polymorphisms and lung cancer risk when all the eligible studies were pooled into the meta-analysis. When we performed subgroup analysis, significantly increased lung cancer risk was observed in Caucasians (− − vs. + +: OR = 1.23, 95% CI: 1.07 to 1.41), Asians (− − vs.− +: OR = 1.24, 95% CI: 1.10 to 1.41; recessive model: OR = 1.45, 95% CI: 1.19 to 1.77; dominant model: OR = 1.53, 95% CI: 1.24 to 1.90), Indians (− − vs. + +: OR = 2.53, 95% CI: 1.61 to 3.98; recessive model: OR = 1.69, 95% CI: 1.07 to 2.67; dominant model: OR = 2.11, 95% CI: 1.36 to 3.28), hospital-based studies, and population-based studies. In summary, this meta-analysis indicates that the combined effects of the GSTM1 and GSTT1 polymorphisms are associated with increased lung cancer risk in Asians, Caucasians, and Indians.

Abstract 436: Mfn2 is a Nodal Point Regulatory Step That Coordinates Angiogenic Phenotype in the Vascular Endothelium

Recent published data suggests that endothelial metabolism regulates angiogenesis. The key regulators of mitochondrial dynamics, mitofusins (Mfn1 and Mfn2) have been linked to cellular metabolic profile in tissues with high energetic requirements but their role in endothelial cells, were mitochondria function as signaling organelles is unknown. Here, we found that Mfn2 modulates postnatal neovascularization. Endothelial deletion of Mfn2 (Mfn2 ecko ) impaired, whereas, endothelial Mfn1 deletion (Mfn1 ecko ) did not affect clinical recovery, limb blood flow reperfusion, and capillary density compared with wild-type mice. These effects were associated with reduced eNOS activation in the ischemic leg of Mfn2 ecko mice compared with wild-type mice. Transplantation of bone marrow cells from WT to Mfn2ecko mice did not significantly improve blood perfusion in the ischemic limb of Mfn2 ecko mice. In agreement with these results, salient features of angiogenesis such as eNOS phosphorylation, cell migration, proliferation and capillary sprout formation were significantly inhibited in Mfn2 null primary mouse lung endothelial cells (Mfn2 -/- MLECs), whereas ablation of Mfn1 did not affect angiogenic signaling following VEGF stimulation. Because Mfn2 modulates the unfolded protein response (UPR) and the UPR machinery has been shown to generate angiomodulatory signals, we ascertained the effects of Mfn2 loss on UPR-mediated VEGF angiogenic signal transduction as potential mechanism. Mfn2 ablation sensitized Mfn2 -/- MLECs to proapototic UPR activation following VEGF treatment according to CHOP levels. Augmented CHOP levels corresponded with reduced eNOS phosphorylation. Inhibition of the UPR PERK signaling axis with PERK siRNA or reconstitution of Mfn2 (AdMfn2) reduced CHOP levels and significantly improved eNOS activation, EC proliferation and migration in Mfn2 -/- MLECs. Moreover, PERK siRNA or reconstitution of Mfn2 rescued the defect in capillary sprout formation in Mfn2 ecko mice. These data suggest that Mfn2 regulate angiogenic signaling in a UPR PERK axis-dependent manner and extend the role of Mfn2 beyond mitochondrial dynamics, metabolism and ER stress to angiogenesis and reparative vascular remodeling.

Abstract 3021: Development of small molecule direct AMPK activators for the treatment of cancer

Abstract 5’-AMP-activated protein kinase (AMPK) is a key sensor of cellular energy status and is critical for maintaining energy homeostasis under conditions of nutrient stress. During cellular transformation, metabolic reprogramming enables the aberrant growth and proliferation of tumor cells. Both positive and negative roles for AMPK in tumor cell proliferation and survival have been reported. However, only a limited number of studies addressed this question with potent direct AMPK activators. AMPK exists as heterotrimers composed of the catalytic subunit α and reguratory subunits β and γ. We expressed the full length of all three human AMPK subunits in insect cells, purified the heterotrimer complexes, and used them for biochemical screening and characterization of AMPK activators. The purified complexes displayed basal activity, which was further enhanced by AMP. The compounds we identified potently activated the complexes in vitro at AC(2X)s (the concentration that gives a twofold activation) of 0.001-0.3 μM. Importantly, the compounds up-regulated substrate phosphorylation (pS79 Acetyl-CoA Carboxylase) and/or auto-phosphorylation (pT172 AMPKα) in multiple cancer cell lines including HepG2 hepatoma cells, A549 liver kinase B1 (LKB1) null lung cancer cells, and MOLM14 myeloid leukemia cells, indicating activation was irrespective of functional status of LKB1, which is a key AMPK-activation kinase. Activation of AMPK by the compounds was also confirmed using native AMPK isolated from normal tissues and tumor cells. We further investigated anti-proliferative effects of the compounds and found that up-regulation of AMPK kinase activity was correlated with anti-proliferative effects in A549 and MOLM14, but not in HepG2, suggesting that positive effects of direct AMPK activators could be cell-type dependent. Interestingly, we identified compounds that display comparable AMPK activation in HepG2 and A549 yet possessed divergent activities on proliferation across a panel of tumor lines. Analysis of cellular signaling across several of these tumor lines with this set of the compounds revealed dose-dependent effects on mTORC1 substrates, feedback signaling to PI3K and mTORC2, and inhibition of kinases downstream of RAF. Direct activation of AMPK could be a good therapeutic strategy for the treatment of subsets of cancers. Citation Format: Yasumichi Hitoshi, Yonchu Jenkins, Yingwu Li, Elmer Sampang, Xiang Xu, Guodong Dong, Jianing Huang, Nan Lin, Dane Goff, Simon Shaw, Luke Boralsky, Rajinder Singh, Sarkiz D. Issakani, Donald G. Payan. Development of small molecule direct AMPK activators for the treatment of cancer. [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 3021.

TP53 Silencing Bypasses Growth Arrest of BRAFV600E-Induced Lung Tumor Cells in a Two-Switch Model of Lung Tumorigenesis.

Lung carcinogenesis is a multistep process in which normal lung epithelial cells are converted to cancer cells through the sequential acquisition of multiple genetic or epigenetic events. Despite the utility of current genetically engineered mouse (GEM) models of lung cancer, most do not allow temporal dissociation of the cardinal events involved in lung tumor initiation and cancer progression. Here we describe a novel two-switch GEM model for BRAF(V600E)-induced lung carcinogenesis allowing temporal dissociation of these processes. In mice carrying a Flp recombinase-activated allele of Braf (Braf(FA)) in conjunction with Cre-regulated alleles of Trp53, Cdkn2a, or c-MYC, we demonstrate that secondary genetic events can promote bypass of the senescence-like proliferative arrest displayed by BRAF(V600E)-induced lung adenomas, leading to malignant progression. Moreover, restoring or activating TP53 in cultured BRAF(V600E)/TP53(Null) or BRAF(V600E)/INK4A-ARF(Null) lung cancer cells triggered a G1 cell-cycle arrest regardless of p19(ARF) status. Perhaps surprisingly, neither senescence nor apoptosis was observed upon TP53 restoration. Our results establish a central function for the TP53 pathway in restricting lung cancer development, highlighting the mechanisms that limit malignant progression of BRAF(V600E)-initiated tumors.

Highlights from Recent Cancer Literature

Highlights from Recent Cancer Literature

Role played by Prx1-dependent extracellular matrix properties in vascular smooth muscle development in embryonic lungs.

Although there are many studies focusing on the molecular pathways underlying lung vascular morphogenesis, the extracellular matrix (ECM)-dependent regulation of mesenchymal cell differentiation in vascular smooth muscle development needs better understanding. In this study, we demonstrate that the paired related homeobox gene transcription factor Prx1 maintains the elastic ECM properties, which are essential for vascular smooth muscle precursor cell differentiation. We have found that Prx1(null) mouse lungs exhibit defective vascular smooth muscle development, downregulated elastic ECM expression, and compromised transforming growth factor (TGF)-β localization and signaling. Further characterization of ECM properties using decellularized lung ECM scaffolds derived from Prx1 mice demonstrated that Prx1 is required to maintain lung ECM stiffness. The results of cell culture using stiffness-controlled 2-D and 3-D synthetic substrates confirmed that Prx1-dependent ECM stiffness is essential for promotion of smooth muscle precursor differentiation for effective TGF-β stimulation. Supporting these results, both decellularized Prx1(null) lung ECM and Prx1(WT) (wild type) ECM scaffolds with blocked TGF-β failed to support mesenchymal cell to 3-D smooth muscle cell differentiation. These results suggest a novel ECM-dependent regulatory pathway of lung vascular development wherein Prx1 regulates lung vascular smooth muscle precursor development by coordinating the ECM biophysical and biochemical properties.

A Role of Myocardin Related Transcription Factor-A (MRTF-A) in Scleroderma Related Fibrosis.

In scleroderma (systemic sclerosis, SSc), persistent activation of myofibroblast leads to severe skin and organ fibrosis resistant to therapy. Increased mechanical stiffness in the involved fibrotic tissues is a hallmark clinical feature and a cause of disabling symptoms. Myocardin Related Transcription Factor-A (MRTF-A) is a transcriptional co-activator that is sequestered in the cytoplasm and translocates to the nucleus under mechanical stress or growth factor stimulation. Our objective was to determine if MRTF-A is activated in the disease microenvironment to produce more extracellular matrix in progressive SSc. Immunohistochemistry studies demonstrate that nuclear translocation of MRTF-A in scleroderma tissues occurs in keratinocytes, endothelial cells, infiltrating inflammatory cells, and dermal fibroblasts, consistent with enhanced signaling in multiple cell lineages exposed to the stiff extracellular matrix. Inhibition of MRTF-A nuclear translocation or knockdown of MRTF-A synthesis abolishes the SSc myofibroblast enhanced basal contractility and synthesis of type I collagen and inhibits the matricellular profibrotic protein, connective tissue growth factor (CCN2/CTGF). In MRTF-A null mice, basal skin and lung stiffness was abnormally reduced and associated with altered fibrillar collagen. MRTF-A has a role in SSc fibrosis acting as a central regulator linking mechanical cues to adverse remodeling of the extracellular matrix.

Glutathione S-transferase θ1 polymorphism contributes to lung cancer susceptibility: A meta-analysis of 26 case-control studies.

The GSTT1 gene encodes a key enzyme involved in the metabolism of xenobiotics and its polymorphisms have been associated with individual susceptibility to various malignancies. Numerous molecular epidemiological studies have been performed to investigate the association between GSTT1 gene polymorphisms and lung cancer susceptibility; however, the results of previous studies were inconsistent. Therefore, the aim of the present study was to conduct a meta-analysis in order to derive a more precise estimation of the association in the East Asian populations. The meta-analysis included 7,415 lung cancer cases and 6,084 controls from 26 published studies in East Asia, which were selected from the PubMed and China National Knowledge Infrastructure databases, up to March 20, 2014. Using crude odds ratios (ORs) with 95% confidence intervals (CIs), a statistically significant association was identified between the GSTT1 null genotype and lung cancer in the East Asian populations (OR=1.17; 95% CI, 1.09–1.25; Pheterogeneity=0.003). Furthermore, subgroup analyses revealed that the lung cancer risk in smokers carrying the GSTT1 null genotype was significantly increased compared with non-smokers (OR=1.71; 95% CI, 1.04–2.81; Pheterogeneity=0.002). Thus, the GSTT1 null genotype may increase the risk of lung cancer among the East Asian populations.

Mutations of p53 and KRAS activate NF-κB to promote chemoresistance and tumorigenesis via dysregulation of cell cycle and suppression of apoptosis in lung cancer cells

Although mutations of p53 and KRAS and activation of NF-κB signaling have been highly associated with chemoresistance and tumorigenesis of lung cancer, the interactive mechanisms between two of p53, KRAS, and NF-κB are elusive. In the present study, we first observed that blocking of NF-κB function in KRAS mutant A549 cell line with an IκBα mutant (IκBαM) inhibited cell cycle progression, anti-apoptosis, chemoresistance, and tumorigenesis. Silencing of p53 or KRAS in A549 or H358 cells either enhanced or attenuated the resistance of cells to cisplatin and taxol through promotion or suppression of the NF-κB p65 nuclear translocation. Introduction of a wild type p53 into p53 null lung cancer cell lines H1299 and H358 inhibited NF-κB activity, leading to the enhanced response to chemotherapeutic drugs. Delivery of a mutant p53 or KRAS-V12 into A549/IκBαM or H1299/p53Wt cells increased cell cycle progression, anti-apoptosis, chemoresistance, and tumorigenesis due to the accumulated nuclear localization of NF-κB p65, while treatment of H1299/p53Wt/KRAS-V12 with NF-κB inhibitor PS1145 diminished these effects. Thus, we conclude that p53 deficiency and KRAS mutation activate the NF-κB signaling to control chemoresistance and tumorigenesis, and that the status of p53 and KRAS may be considered for the targeted therapy against NF-κB in lung cancer patients.

GSTM1 polymorphisms and lung cancer risk in the Chinese population: a meta-analysis based on 47 studies.

Although a number of studies have been conducted on the association between GSTM1 polymorphisms and lung cancer in China, this association remains elusive and controversial. To clarify the effects of GSTM1 polymorphisms on the risk of lung cancer, a meta-analysis was performed in the Chinese population. Related studies were identified from PubMed, Springer Link, Ovid, Chinese Wanfang Data Knowledge Service Platform, Chinese National Knowledge Infrastructure (CNKI), and Chinese Biology Medicine (CBM) up to 5th April 2014. A total of 45 articles (47 studies) including 6,623 cases and 7,865 controls were involved in this meta-analysis. Overall, a significant association (OR = 1.45, 95%CI: 1.32-1.60) was found between the null GSTM1 and lung cancer risk when all studies in Chinese population pooled into the meta-analysis. In subgroup analyses stratified by quality score, geographic area and source of controls, the same results were observed under all the models. This meta-analysis showed that the null GSTM1 may be a potential biomarker for lung cancer risk in Chinese, but further studies with gene-gene and gene-environment interactions are required for definite conclusions.

Abstract 591: LKB1 regulates COX-2 transcription via CRTCs dependent pathway

Abstract Inactivation of the liver kinase B1 (LKB1) gene by somatic mutation is a common event in lung adenocarcinoma. LKB1 was first identified as a tumor suppressor responsible for Peutz-Jeghers syndrome (PJS) and up regulation of cyclooxygenase-2 (COX-2) was detected in a significant percentage of human PJS polyps. In addition, COX-2 has been proposed as a therapeutic target for lung cancer although clinical trial using COX-2 inhibitors have been disappointing. In the current study, we identified a novel LKB1/CRTC/COX-2 molecular pathway in human lung cancer cells and provided new information for clinical use of COX-2 inhibitors. The Kaye lab cloned the CREB-regulated transcription co-activators (CRTCs) and showed aberrant phosphorylation and activation of CRTC1 exclusively in non-small cell lung cancer (NSCLC) samples carrying LKB1 null mutations. We have now demonstrated that CRTC directly regulates COX-2 expression via evolutionarily conserved CRE sites within the promoter. In addition, we observed that ectopic expression of LKB1 resulted in nuclear export of phosphorylated CRTC with attenuation of COX-2 expression. Alternatively, LKB1 knock-down results in CRTC activation and promotes COX-2 expression in NSCLC cells. Importantly, LKB1 null lung cancer cells were preferentially sensitive to COX-2 inhibitors. In summary, our data defines a CRTCs-mediated transcriptional regulatory mechanism for COX-2 activity in cancer and proposes a possible clinical application of COX-2 inhibitors in patients with lung tumors carrying somatic LKB1 null mutations. Citation Format: Chunxia Cao, Ruli Gao, Min Zhang, Zirong Chen, Lizi Wu, Maria Zajac Kaye, Frederic Kaye. LKB1 regulates COX-2 transcription via CRTCs dependent pathway. [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 591. doi:10.1158/1538-7445.AM2014-591