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The alveolar epithelial glycocalyx is a dense anionic layer of glycosaminoglycans (GAGs) and proteoglycans that lines the apical surface of the alveolar epithelium. In contrast to the pulmonary endothelial glycocalyx, which has well-established roles in vascular homeostasis and septic organ dysfunction, the alveolar epithelial glycocalyx is less understood. Recent preclinical studies demonstrated that the epithelial glycocalyx is degraded in multiple murine models of acute respiratory distress syndrome (ARDS), particularly those that result from inhaled insults (so-called “direct” lung injury), leading to shedding of GAGs into the alveolar airspaces. Epithelial glycocalyx degradation also occurs in humans with respiratory failure, as quantified by analysis of airspace fluid obtained from ventilator heat moisture exchange (HME) filters. In patients with ARDS, GAG shedding correlates with the severity of hypoxemia and is predictive of the duration of respiratory failure. These effects may be mediated by surfactant dysfunction, as targeted degradation of the epithelial glycocalyx in mice was sufficient to cause increased alveolar surface tension, diffuse microatelectasis, and impaired lung compliance. In this review, we describe the structure of the alveolar epithelial glycocalyx and the mechanisms underlying its degradation during ARDS. We additionally review the current state of knowledge regarding the attributable effect of epithelial glycocalyx degradation in lung injury pathogenesis. Finally, we address glycocalyx degradation as a potential mediator of ARDS heterogeneity, and the subsequent value of point-of-care quantification of GAG shedding to potentially identify patients who are most likely to respond to pharmacological agents aimed at attenuating glycocalyx degradation.

Acute respiratory distress syndrome (ARDS) is a common and life-threatening cause of respiratory failure. Despite decades of research, there are no effective pharmacologic therapies to treat this disease process and mortality remains high. The shortcomings of prior translational research efforts have been increasingly attributed to the heterogeneity of this complex syndrome, which has led to an increased focus on elucidating the mechanisms underlying the interpersonal heterogeneity of ARDS. This shift in focus aims to move the field towards personalized medicine by defining subgroups of ARDS patients with distinct biology, termed endotypes, to quickly identify patients that are most likely to benefit from mechanism targeted treatments. In this review, we first provide a historical perspective and review the key clinical trials that have advanced ARDS treatment. We then review the key challenges that exist with regards to the identification of treatable traits and the implementation of personalized medicine approaches in ARDS. Lastly, we discuss potential strategies and recommendations for future research that we believe will aid in both understanding the molecular pathogenesis of ARDS and the development of personalized treatment approaches.

Acute Respiratory Distress Syndrome (ARDS) is a devastating disease process that involves dysregulated inflammation and decreased alveolar-capillary barrier function. Despite increased understanding of the pathophysiology, no effective targeted therapies exist to treat ARDS. Recent preclinical studies suggest that the multi-tyrosine kinase inhibitor, imatinib, which targets the Abl kinases c-Abl and Arg, has the potential to restore endothelial dysfunction caused by inflammatory agonists. Prior work demonstrates that imatinib attenuates LPS (lipopolysaccharide)-induced vascular leak and inflammation; however, the mechanisms underlying these effects remain incompletely understood. In the current study, we demonstrate that imatinib inhibits LPS-induced increase in the phosphorylation of CrkL, a specific substrate of Abl kinases, in human pulmonary endothelial cells. Specific silencing of Arg, and not c-Abl, attenuated LPS-induced pulmonary vascular permeability as measured by electrical cellular impedance sensing (ECIS) and gap formation assays. In addition, direct activation of Abl family kinases with the small molecule activator DPH resulted in endothelial barrier disruption that was attenuated by Arg siRNA. In complementary studies to characterize the mechanisms by which Arg mediates endothelial barrier function, Arg silencing was found to inhibit LPS-induced disruption of adherens junctions and phosphorylation of myosin light chains (MLC). Overall, these results characterize the mechanisms by which imatinib protects against LPS-induced endothelial barrier disruption and suggest that Arg inhibition may represent a novel strategy to enhance endothelial barrier function.

Acute lung injury/acute respiratory distress syndrome (ALI/ARDS), an illness characterized by life-threatening vascular leak, is a significant cause of morbidity and mortality in critically ill patients. Recent preclinical studies and clinical observations have suggested a potential role for the chemotherapeutic agent imatinib in restoring vascular integrity. Our prior work demonstrates differential effects of imatinib in mouse models of ALI, namely attenuation of LPS-induced lung injury but exacerbation of ventilator-induced lung injury (VILI). Because of the critical role of mechanical ventilation in the care of patients with ARDS, in the present study we pursued an assessment of the effectiveness of imatinib in a “two-hit” model of ALI caused by combined LPS and VILI. Imatinib significantly decreased bronchoalveolar lavage protein, total cells, neutrophils, and TNF-α levels in mice exposed to LPS plus VILI, indicating that it attenuates ALI in this clinically relevant model. In subsequent experiments focusing on its protective role in LPS-induced lung injury, imatinib attenuated ALI when given 4 h after LPS, suggesting potential therapeutic effectiveness when given after the onset of injury. Mechanistic studies in mouse lung tissue and human lung endothelial cells revealed that imatinib inhibits LPS-induced NF-κB expression and activation. Overall, these results further characterize the therapeutic potential of imatinib against inflammatory vascular leak.

Cortactin translocates to the cell periphery in vascular endothelial cells (ECs) on cortical-actin assembly in response to pulsatile shear stress. Because cortactin has putative sites for AMP-activated protein kinase (AMPK) phosphorylation and sirtuin 1 (SIRT1) deacetylation, we examined the hypothesis that AMPK and SIRT1 coregulate cortactin dynamics in response to shear stress.Analysis of the ability of AMPK to phosphorylate recombinant cortactin and oligopeptides whose sequences matched AMPK consensus sequences in cortactin pointed to Thr-401 as the site of AMPK phosphorylation. Mass spectrometry confirmed Thr-401 as the site of AMPK phosphorylation. Immunoblot analysis with AMPK siRNA and SIRT1 siRNA in human umbilical vein ECs and EC-specific AMPKα2 knockout mice showed that AMPK phosphorylation of cortactin primes SIRT1 deacetylation in response to shear stress. Immunoblot analyses with cortactin siRNA in human umbilical vein ECs, phospho-deficient T401A and phospho-mimetic T401D mutant, or aceto-deficient (9K/R) and aceto-mimetic (9K/Q) showed that cortactin regulates endothelial nitric oxide synthase activity. Confocal imaging and sucrose-density gradient analyses revealed that the phosphorylated/deacetylated cortactin translocates to the EC periphery facilitating endothelial nitric oxide synthase translocation from lipid to nonlipid raft domains. Knockdown of cortactin in vitro or genetic reduction of cortactin expression in vivo in mice substantially decreased the endothelial nitric oxide synthase-derived NO bioavailability. In vivo, atherosclerotic lesions increase in ApoEAMPK phosphorylation of cortactin followed by SIRT1 deacetylation modulates the interaction of cortactin and cortical-actin in response to shear stress. Functionally, this AMPK/SIRT1 coregulated cortactin-F-actin dynamics is required for endothelial nitric oxide synthase subcellular translocation/activation and is atheroprotective.

IntroductionPseudogenes are paralogues of functional genes historically viewed as defunct due to either the lack of regulatory elements or the presence of frameshift mutations. Recent evidence, however, suggests that pseudogenes may regulate gene expression, although the functional role of pseudogenes remains largely unknown. We previously reported that MYLKP1, the pseudogene of MYLK that encodes myosin light chain kinase (MLCK), is highly expressed in lung and colon cancer cell lines and tissues but not in normal lung or colon. The MYLKP1 promoter is minimally active in normal bronchial epithelial cells but highly active in lung adenocarcinoma cells. In this study, we further validate MYLKP1 as an oncogene via elucidation of the functional role of MYLKP1 genetic variants in colon cancer risk.MethodsProliferation and migration assays were performed in MYLKP1-transfected colon and lung cancer cell lines (H441, A549) and commercially-available normal lung and colon cells. Fourteen MYLKP1 SNPs (MAFs >0.01) residing within the 4 kb MYLKP1 promoter region, the core 1.4 kb of MYLKP1 gene, and a 4 kb enhancer region were selected and genotyped in a colorectal cancer cohort. MYLKP1 SNP influences on activity of MYLKP1 promoter (2kb) was assessed by dual luciferase reporter assay.ResultsCancer cell lines, H441 and A549, exhibited increased MYLKP1 expression, increased MYLKP1 luciferase promoter activity, increased proliferation and migration. Genotyping studies identified two MYLKP1 SNPs (rs12490683; rs12497343) that significantly increase risk of colon cancer in African Americans compared to African American controls. Rs12490683 and rs12497343 further increase MYLKP1 promoter activity compared to the wild type MYLKP1 promoter.ConclusionMYLKP1 is a cancer-promoting pseudogene whose genetic variants differentially enhance cancer risk in African American populations.

Endothelial dysfunction underlies the pathophysiology of vascular disorders such as acute lung injury (ALI) syndromes. Recent work has identified the Abl family kinases (c-Abl and Arg) as important regulators of endothelial cell (EC) barrier function and suggests that their inhibition by currently available pharmaceutical agents such as imatinib may be EC protective. Here we describe novel and differential effects of imatinib in regulating lung pathophysiology in two clinically relevant experimental models of ALI. Imatinib attenuates endotoxin (LPS)-induced vascular leak and lung inflammation in mice but exacerbates these features in a mouse model of ventilator-induced lung injury (VILI). We next explored these discrepant observations in vitro through investigation of the roles for Abl kinases in cultured lung EC. Imatinib attenuates LPS-induced lung EC permeability, restores VE-cadherin junctions, and reduces inflammation by suppressing VCAM-1 expression and inflammatory cytokine (IL-8 and IL-6) secretion. Conversely, in EC exposed to pathological 18% cyclic stretch (CS) (in vitro model of VILI), imatinib decreases VE-cadherin expression, disrupts cell-cell junctions, and increases IL-8 levels. Downregulation of c-Abl expression with siRNA attenuates LPS-induced VCAM-1 expression, whereas specific reduction of Arg reduces VE-cadherin expression in 18% CS-challenged ECs to mimic the imatinib effects. In summary, imatinib exhibits pulmonary barrier-protective and anti-inflammatory effects in LPS-injured mice and lung EC; however, imatinib exacerbates VILI as well as dysfunction in 18% CS-EC. These findings identify the Abl family kinases as important modulators of EC function and potential therapeutic targets in lung injury syndromes.

Patients with acute respiratory distress syndrome (ARDS) exhibit elevated levels of interleukin-6 (IL-6), which correlate with increased morbidity and mortality. The exact role of IL-6 in ARDS has proven difficult to study because it exhibits either pro- or anti-inflammatory actions in mouse models of lung injury, depending on the model utilized. In order to improve understanding of the role of this complex cytokine in ARDS, we evaluated IL-6 using the clinically relevant combination of lipopolysaccharide (LPS) and ventilator-induced lung injury (VILI) in IL-6(-/-) mice. Bronchoalveolar lavage fluid (BAL), whole-lung tissue, and histology were evaluated for inflammatory markers of injury. Transendothelial electrical resistance was used to evaluate the action of IL-6 on endothelial cells in vitro. In wild-type mice, the combination model showed a significant increase in lung injury compared to either LPS or VILI alone. IL-6(-/-) mice exhibited a statistically significant decrease in BAL cellular inflammation as well as lower histologic scores for lung injury, changes observed only in the combination model. A paradoxical increase in BAL total protein was observed in IL-6(-/-) mice exposed to LPS, suggesting that IL-6 provides protection from vascular leakage. However, in vitro data showed that IL-6, when combined with its soluble receptor, actually caused a significant increase in endothelial cell permeability, suggesting that the protection seen in vivo was likely due to complex interactions of IL-6 and other inflammatory mediators rather than to direct effects of IL-6. These studies suggest that a dual-injury model exhibits utility in evaluating the pleiotropic effects of IL-6 in ARDS on inflammatory cells and lung endothelium.

Pulmonary endothelial cell (EC) barrier dysfunction and recovery is critical to the pathophysiology of acute respiratory distress syndrome. Cytoskeletal and subsequent cell membrane dynamics play a key mechanistic role in determination of EC barrier integrity. Here, we characterizAQe the actin related protein 2/3 (Arp 2/3) complex, a regulator of peripheral branched actin polymerization, in human pulmonary EC barrier function through studies of transendothelial electrical resistance (TER), intercellular gap formation, peripheral cytoskeletal structures and lamellipodia. Compared to control, Arp 2/3 inhibition with the small molecule inhibitor CK-666 results in a reduction of baseline barrier function (1,241 ± 53 vs 988 ± 64 ohm; p

Radiotherapy as a primary treatment for thoracic malignancies induces deleterious effects, such as acute or subacute radiation-induced lung injury (RILI). Although the molecular etiology of RILI is controversial and likely multifactorial, a potentially important cellular target is the lung endothelial cytoskeleton that regulates paracellular gap formation and the influx of macromolecules and fluid to the alveolar space. Here we investigate the central role of a key endothelial cytoskeletal regulatory protein, the nonmuscle isoform of myosin light chain kinase (nmMLCK), in an established murine RILI model. Our results indicate that thoracic irradiation significantly augmented nmMLCK protein expression and enzymatic activity in murine lungs. Furthermore, genetically engineered mice harboring a deletion of the nmMLCK gene (nmMLCK(-/-) mice) exhibited protection from RILI, as assessed by attenuated vascular leakage and leukocyte infiltration. In addition, irradiated wild-type mice treated with two distinct MLCK enzymatic inhibitors, ML-7 and PIK (peptide inhibitor of kinase), also demonstrated attenuated RILI. Taken together, these data suggests a key role for nmMLCK in vascular barrier regulation in RILI and warrants further examination of RILI strategies that target nmMLCK.

In addition to superoxide (O2 .-) generation from nitric oxide synthase (NOS) oxygenase domain, a new O2 .- generation site has been identified in the reductase domain of inducible NOS (iNOS) and neuronal NOS (nNOS). Cysteine S-glutathionylation in eNOS reductase domain also induces O2 .- generation from eNOS reductase domain. However, the characteristics and regulatory mechanism of the O2 .- generation from NOS reductase domain remain unclear. We cloned and purified the wild type bovine eNOS (WT eNOS), a mutant of Serine 1179 replaced with aspartic acid eNOS (S1179D eNOS), which mimics the negative charge caused by phosphorylationand truncated eNOS reductase domain (eNOS RD). Both WT eNOS and S1179D eNOS generated significant amount of O2 .- in the absence of BH4 and L-arginine. The capacity of O2 .- generation from S1179D eNOS was significantly higher than that of WT eNOS (1.74:1). O2 .- generation from both WT eNOS and S1179D eNOS were not completely inhibited by 100nM tetrahydrobiopterin(BH4). This BH4 un-inhibited O2 .- generation from eNOS was blocked by 10mM flavoprotein inhibitor, diphenyleneiodonium (DPI). Purified eNOS reductase domain protein confirmed that this BH4 un-inhibited O2 .- generation originates at the FMN or FAD/NADPH binding site of eNOS reductase domain. DEPMPO-OOH adduct EPR signals and NADPH consumptions analyses showed that O2 .- generation from eNOS reductase domain was regulated by Serine 1179 phosphorylation and DPI, but not by L-arginine, BH4 or calmodulin (CaM). In addition to the heme center of eNOS oxygenase domain, we confirmed another O2 .- generation site in the eNOS reductase domain and characterized its regulatory properties.

Introduction: Acute lung injury (ALI) is characterized by inflammation-induced disruption of the endothelial cell (EC) barrier lining the pulmonary vasculature, which causes leakage of fluid and inflammatory cells into the airspaces. The mechanisms underlying ALI are critically dependent on EC cytoskeletal regulation of vascular permeability. The Abl family kinases Abl and Abl Related Gene (Arg) are key mediators of the endothelial cytoskeleton. The pharmaceutical agent imatinib inhibits these kinases and is used clinically for the treatment of multiple different malignancies. Hypothesis: Imatinib attenuates LPS-induced inflammation and vascular leakage in murine ALI and retains its protective properties when combined with high tidal volume (Tv) mechanical ventilation (MV). Methods: As a clinically relevant combination model of ALI stimuli, animals were given intratracheal (i.t) LPS (0.5mg/kg) (vs. PBS), allowed to recover for 20 hours, and then intubated for MV (Tv 30ml/kg, RR 75/min, PEEP 0 cm H2O, 4hrs). Imatinib (75mg/kg) (vs. vehicle) was given i.p. 30 min before LPS and 30 min before MV. For post-injury experiments, imatinib (75mg/kg) (vs. vehicle) was given 4 hours after LPS (1mg/kg) and animals were harvested after 18 hrs. Bronchoalveolar lavage fluid (BAL) was analyzed for total cell counts, neutrophil number, total protein, albumin content, and cytokine levels. Lung tissues were used for MPO activity, albumin content, histology, and Evans Blue dye extravasation. Results: Imatinib attenuated inflammation in both combination model studies and post-LPS treatment studies as measured by BAL cell count, PMN number, MPO activity, TNFα levels, and H&E staining. Additionally, in both models, imatinib decreased vascular leakage as measured by total protein, BAL and lung tissue albumin, and Evans Blue dye extravasation. Conclusions: Imatinib attenuates LPS-induced inflammation and vascular leak in mice. Additionally, imatinib is protective in a clinically relevant murine model of combined LPS and mechanical ventilation injury. Imatinib may have potential for translational use in ALI patients.

Whereas infection or immunization of humans/primates with microbes coproducing HMBPP/IPP can remarkably activate Vγ2Vδ2 T cells, in vivo studies have not been done to dissect HMBPP- and IPP-driven expansion, pulmonary trafficking, effector functions, and memory polarization of Vγ2Vδ2 T cells. We define these phosphoantigen-host interplays by comparative immunizations of macaques with the HMBPP/IPP-coproducing Listeria ΔactA prfA* and HMBPP-deficient Listeria ΔactAΔgcpEprfA* mutant. The HMBPP-deficient ΔgcpE mutant shows lower ability to expand Vγ2Vδ2 T cells in vitro than the parental HMBPP-producing strain but displays comparably attenuated infectivity or immunogenicity. Respiratory immunization of macaques with the HMBPP-deficient mutant elicits lower pulmonary and systemic responses of Vγ2Vδ2 T cells compared with the HMBPP-producing vaccine strain. Interestingly, HMBPP-deficient mutant reimmunization or boosting elicits enhanced responses of Vγ2Vδ2 T cells, but the magnitude is lower than that by HMBPP-producing listeria. HMBPP-deficient listeria differentiated fewer Vγ2Vδ2 T effector cells capable of coproducing IFN-γ and TNF-α and inhibiting intracellular listeria than HMBPP-producing listeria. Furthermore, HMBPP deficiency in listerial immunization influences memory polarization of Vγ2Vδ2 T cells. Thus, both HMBPP and IPP production in listerial immunization or infection elicit systemic/pulmonary responses and differentiation of Vγ2Vδ2 T cells, but a role for HMBPP is more dominant. Findings may help devise immune intervention.

Disruption of the pulmonary endothelial barrier and subsequent vascular leak is a hallmark of acute lung injury. Dynamic rearrangements in the endothelial cell (EC) peripheral membrane and underlying cytoskeleton are critical determinants of barrier function. The cytoskeletal effector protein non-muscle myosin light chain kinase (nmMLCK) and the actin-binding regulatory protein cortactin are important regulators of the endothelial barrier. In the present study we functionally characterize a proline-rich region of nmMLCK previously identified as the possible site of interaction between nmMLCK and cortactin. A mutant nmMLCK construct deficient in proline residues at the putative sites of cortactin binding (amino acids 973, 976, 1019, 1022) was generated. Co-immunoprecipitation studies in human lung EC transfected with wild-type or mutant nmMLCK demonstrated similar levels of cortactin interaction at baseline and after stimulation with the barrier-enhancing agonist, sphingosine 1-phosphate (S1P). In contrast, binding studies utilizing recombinant nmMLCK fragments containing the wild-type or proline-deficient sequence demonstrated a two-fold increase in cortactin binding (p0.01) to the mutant construct. Immunofluorescent microscopy revealed an increased stress fiber density in ECs expressing GFP-labeled mutant nmMLCK at baseline (p=0.02) and after thrombin (p=0.01) or S1P (p=0.02) when compared to wild-type. Mutant nmMLCK demonstrated an increase in kinase activity in response to thrombin (p0.01). Kymographic analysis demonstrated an increased EC membrane retraction distance and velocity (p0.01) in response to the barrier disrupting agent thrombin in cells expressing the mutant vs. the wild-type nmMLCK construct. These results provide evidence that critical prolines within nmMLCK (amino acids 973, 976, 1019, 1022) regulate cytoskeletal and membrane events associated with pulmonary endothelial barrier function.

Bronchial epithelial junctions provide not only a physical barrier, but also an immune barrier against the allergens of asthma. Epithelial junction integrity is closely related to the severity and progression of asthma. The bronchial epithelial barrier consists of tight junctions, adherens junctions, desmosomes, hemidesmosomes and gap junctions, all of which are potentially implicated in asthma pathophysiology. In tight junctions, claudins, occludens, ZO-1 and β-catenin expression have been shown to be decreased by asthma allergens, resulting tight junction disruption. Similarly, E-cadherin and α-catenin levels have also been reported to be dysregulated in response to asthma allergens, resulting in alterations in adherens junction structure. Asthma allergens also alter desmosome and hemidesmosome structure; however, no reports have shown that desmosome or hemidesmosome junction protein expression is altered in response to asthma allergens. Finally, in gap junctions, connexin 37 mRNA and protein were found to be decreased in the ovalbumin (OVA) induced allergic model. In summary, the regulation of bronchial junction protein expression and structure is an important and presently understudied component of asthma pathophysiology. We believe that further investigation in this area has the potential to aid in the development of novel asthma treatments.

Rationale Acute respiratory distress syndrome (ARDS) is a life-threatening disease process in which overwhelming inflammation causes disruption of the pulmonary endothelial cell (EC) barrier, leading to leakage of fluid and inflammatory cells from the blood stream into the airspaces. Current research aims to identify agents that could both decrease inflammation and increase pulmonary vascular barrier integrity. Recently published work suggests that imatinib, an FDA-approved Abl family kinase inhibitor, may attenuate vascular leak and inflammation; however the mechanism underlying these effects is not completely understood. In the present study we explored the effects of LPS on the expression of the Abl family kinases, c-Abl and Arg, as well as the effects of Abl family kinases on LPS-induced vascular permeability and inflammation. Methods In silico analyses of the promoter regions of Abl1 (encodes c-Abl) and Abl2 (encodes Arg) were analyzed for potential responsive elements using the online programs Genomatix, TFsearch, and Jaspar. Cultured human pulmonary artery ECs were challenged with LPS (100 ng/mL, 24 hrs), harvested using RNeasy kit and reverse transcribed to cDNA. RT-PCR was performed to assess alterations in the expression of Abl1 and Abl2 after LPS challenge. In separate studies, siRNA was used to selectively silence either c-Abl or Arg and inter-endothelial gap formation was assessed by measuring FITC-dextran binding to a biotinylated avidin substrate. Complementary immunofluorescence studies were carried out to assess effects on adherens junction distributions. Western blotting was used to assess the effects of c-Abl and Arg silencing on NFkB phosphorylation. Results In silico analyses revealed that c-Abl contains two antioxidant responsive elements, whereas Arg contains two mechanical stress responsive elements. LPS treatment caused an increase in the mRNA expression of c-Abl (1.5 fold, p Conclusions The Abl family kinases c-Abl and Arg play complementary but distinct roles in mediating vascular permeability and inflammation following LPS challenge. The promoter of Abl1 (c-Abl) contains antioxidant response elements and LPS causes an increase in c-Abl expression. Additionally, LPS increases the mRNA expression of c-Abl, but not Arg. C-Abl contributes to LPS-induced NFκB signaling; whereas Arg contributes to inter-endothelial gap formation and adherens junction stability. Inhibition of both of these kinases may be of benefit in patients with ARDS.

e22051 Background: Treatment of non-small cell lung cancer remains a clinical challenge despite the migration from cytotoxic chemotherapies to targeted agents. Myosin light chain kinase (MLCK) is a protein involved in phosphorylation of regulatory chains of myosin, thereby regulating the contraction of myosin II. The 210 KDa non-muscle MLCK isoform (nmMLCK), expressed in endothelial cells, regulates cell shape and motility, and increases EGFR-mediated proliferation of hepatocytes. Furthermore, inhibitors of MLCK such as ML-7 and ML-9 have been shown to decrease invasiveness of pancreatic prostate cancer cell lines. Clinically, levels of MLCK gene (MYLK) mRNA correlate with increased risk of disease recurrence and development of distant metastasis in lung cancer. These data suggest a potential role for MLCK in lung cancer tumorigenesis and metastasis. Methods: H-23 and H-441 human lung adenocarcinoma cell lines were treated for 12hrs with MLCK chemical inhibitor, ML-7 (20uM), and harvested at 24hr, 48hr, and 72hr for MTS Assay. Cell proliferation was assessed with MTS Assay per manufacturer protocol (Promega). H-23 cells were transiently transfected with a FLAG-tagged (WT) nmMLCK overexpression vector using Fugene Transfection Kit per manufacturer protocol (Promega). Results: While no significant difference in proliferation was noted in A-549 cells, both H-23 and H-441 cells showed a decrease in cell proliferation with inhibition of MLCK. H-23 cells also showed an increase in proliferation when transiently transfected with an MLCK-overexpression vector. Conclusions: Inhibition of endogenous nmMLCK decreases H-23 and H-441 proliferation. Conversely, an increase in nmMLCK expression in vitro increases cell proliferation in H23 cells. These results suggest that MLCK/MYLK may participate in regulation of lung adenocarcinoma cell proliferation.