Non-Small Cell Lung Cancer-Tumor Biology

Lung cancer is one of the leading causes of cancer-related mortality worldwide among men and women [...].

Abstract 2350: Role of ECM hyaluronic acid in the tumor-promoting functions of TIMP-1

Non-small cell lung carcinoma (NSCLC) is responsible for the most significant number of lung cancer deaths with over 85% of lung cancers falling in this category. The dismal outcomes of this disease are augmented by advanced disease at initial presentation and ongoing development of chemoresistance following standard chemotherapeutic interventions. Tissue Inhibitor of metalloproteinase-1 (TIMP-1), one of the natural inhibitors of matrix degrading enzymes, is classically regarded as a tumor suppressor. However, there is much evidence that has established this molecule as having tumorigenic functions and has been shown to be upregulated in multiple cancers as well as in the development of fibrosis. In earlier studies we have demonstrated the tumor-promoting role of TIMP-1 in multiple biological interactions including angiogenesis, apoptosis, chemoresistance and cancer metabolism in NSCLC. The ECM plays an important role in providing structural support and as a depot for growth factors and cytokines critical for cell signaling. As TIMP-1 remains a vital molecule facilitating and modulating multiple elements of the ECM, we have sought to further define its role in the tumor microenvironment ECM in NSCLC cells. Our investigations have shown that TIMP-1 protein accumulates in the culture medium over long incubation periods. We have also found TIMP1 mRNA upregulation during this incubation period and correlated this as a function of cell density. As high cell density led to increased upregulation of TIMP1 mRNA, we postulated that factors secreted in the culture were responsible for this upregulation. We have identified that hyaluronic acid (HA), a component of the ECM, was accumulating in the culture media, resulting in the above response. HA is a critical matrix molecule of the tumor pericellular stroma and its upregulation is associated with poor prognosis. It is synthesized by hyaluronic acid synthetase (HAS) isoforms 1,2 and 3. We have also found that HAS2 was strongly expressed in high TIMP1 expressing NSCLC cells. Several studies have shown increased HAS2 expression in tumor tissue. We found that knocking down TIMP1 resulted in lower HA levels and decreased expression of HAS2. In a 3D coculture spheroid assay utilizing A549 cells and MRC5, we have shown increased expression of TIMP-1 and HA, which was also confirmed in archived NSCLC patient samples. The role of HA in the tumor-promoting functions of TIMP1 will be discussed further.

Citation Format: Nithyananda Thorenoor, Wei Xiao, Amyn M. Rojiani, Mumtaz V. Rojiani. Role of ECM hyaluronic acid in the tumor-promoting functions of TIMP-1 [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 2350.

TIMP-1 Dependent Modulation of Metabolic Profiles Impacts Chemoresistance in NSCLC

The development of chemoresistance remains a significant barrier to treating NSCLC. Alteration of cancer cell metabolism is an important mechanism for chemoresistance. This study explored the role of aberrant metabolism in TIMP-1-mediated chemoresistance. Bioinformatics analysis identified an association of high TIMP-1 with altered energy metabolism. We have defined the role of depolarized mitochondria through a reduction in lactate secretion, higher ROS levels in TIMP-1 KD cells and reduced GSH levels. TIMP-1 modulates the metabolic profile via acetylation of mitochondrial STAT3 and its interaction with CD44. Intriguingly, monomers of acetylated STAT3 were critical for altered metabolism, whereas STAT3 dimers abrogated this function. Further, the mitochondrial metabolic profile was also altered in a cisplatin-resistant clone of A549 cells. We also correlated the immunoexpression of CD44, STAT3 and TIMP-1 in patient samples. This study provided evidence that TIMP-1 alters the metabolic profile by modulating mitochondrial metabolism via the CD44-STAT3 axis through its effects on STAT3 acetylation. It also lent further support to the critical role of TIMP-1 in chemoresistance. Interrogation of the TCGA-LUAD dataset revealed perturbations in the critical modulator that can alter metabolic states in cancer cells. Higher expression of a five-gene signature, including TIMP-1, correlated with immunosuppressive cells and was found to be associated with overall survival. This study identified several metabolic mechanisms that could influence therapeutic options and prognosis in NSCLC patients.

Gene signatures with therapeutic value: emerging perspective for personalized immunotherapy in renal cancer

Renal cancer is one of the deadliest urogenital diseases. In recent years, the advent of immunotherapy has led to significant improvement in the management of patients with renal cancer. Although cancer immunotherapy and its combinations had benefited numerous patients, several challenges need to be addressed. Apart from the high costs of treatment, the lack of predictive biomarkers and toxic side-effects have impeded its wider applicability. To address these issues, new biomarkers are required to predict responsiveness and design personalized treatment strategies. Recent advances in the field of single-cell sequencing and multi-dimensional spatial transcriptomics have identified clinically relevant subtypes of renal cancer. Furthermore, there is emerging potential for gene signatures based on immune cells, non-coding RNAs, and pathways such as metabolism and RNA modification. In this review article, we have discussed recent progress in the identification of gene signatures with predictive and prognostic potential in renal cancer.

Natural Killer Cells and Dendritic Cells: Expanding Clinical Relevance in the Non-Small Cell Lung Cancer (NSCLC) Tumor Microenvironment

Non-small cell lung cancer (NSCLC) is a major subtype of lung cancer that accounts for almost 85% of lung cancer cases worldwide. Although recent advances in chemotherapy, radiotherapy, and immunotherapy have helped in the clinical management of these patients, the survival rate in advanced stages remains dismal. Furthermore, there is a critical lack of accurate prognostic and stratification markers for emerging immunotherapies. To harness immune response modalities for therapeutic benefits, a detailed understanding of the immune cells in the complex tumor microenvironment (TME) is required. Among the diverse immune cells, natural killer (NK cells) and dendritic cells (DCs) have generated tremendous interest in the scientific community. NK cells play a critical role in tumor immunosurveillance by directly killing malignant cells. DCs link innate and adaptive immune systems by cross-presenting the antigens to T cells. The presence of an immunosuppressive milieu in tumors can lead to inactivation and poor functioning of NK cells and DCs, which results in an adverse outcome for many cancer patients, including those with NSCLC. Recently, clinical intervention using modified NK cells and DCs have shown encouraging response in advanced NSCLC patients. Herein, we will discuss prognostic and predictive aspects of NK cells and DC cells with an emphasis on NSCLC. Additionally, the discussion will extend to potential strategies that seek to enhance the anti-tumor functionality of NK cells and DCs.

Prognostic and therapeutic implications of extracellular matrix associated gene signature in renal clear cell carcinoma

Complex interactions in tumor microenvironment between ECM (extra-cellular matrix) and cancer cell plays a central role in the generation of tumor supportive microenvironment. In this study, the expression of ECM-related genes was explored for prognostic and immunological implication in clear cell renal clear cell carcinoma (ccRCC). Out of 964 ECM genes, higher expression (z-score > 2) of 35 genes showed significant association with overall survival (OS), progression-free survival (PFS) and disease-specific survival (DSS). On comparison to normal tissue, 12 genes (NUDT1, SIGLEC1, LRP1, LOXL2, SERPINE1, PLOD3, ZP3, RARRES2, TGM2, COL3A1, ANXA4, and POSTN) showed elevated expression in kidney tumor (n = 523) compared to normal (n = 100). Further, Cox proportional hazard model was utilized to develop 12 genes ECM signature that showed significant association with overall survival in TCGA dataset (HR = 2.45; 95% CI [1.78-3.38]; p < 0.01). This gene signature was further validated in 3 independent datasets from GEO database. Kaplan-Meier log-rank test significantly associated patients with elevated expression of this gene signature with a higher risk of mortality. Further, differential gene expression analysis using DESeq2 and principal component analysis (PCA) identified genes with the highest fold change forming distinct clusters between ECM-rich high-risk and ECM-poor low-risk patients. Geneset enrichment analysis (GSEA) identified significant perturbations in homeostatic kidney functions in the high-risk group. Further, higher infiltration of immunosuppressive T-reg and M2 macrophages was observed in high-risk group patients. The present study has identified a prognostic signature with associated tumor-promoting immune niche with clinical utility in ccRCC. Further exploration of ECM dynamics and validation of this gene signature can assist in design and application of novel therapeutic approaches.

Immunogenomic Gene Signature of Cell-Death Associated Genes with Prognostic Implications in Lung Cancer

Simple Summary

The human body consists of trillions of cells and several million of them die daily. These natural processes which determine the fate of a cell in the human body can be broadly defined as programmed cell death (apoptosis and autophagy) and a non-programmed, passive cell death (necrosis). The inherent genetic diversity in humans and differential expression of mRNAs belonging to these cell death pathways can provide clinically actionable information. In this study, we have discovered a differential 21-gene cell death signature that significantly separates lung cancer patients based on their survival. The patients with increased expression of this genomic signature were found to be at higher risk of dying early. Interestingly, this patient group showed significant perturbations in the expression of cytokines and infiltration of immune cells within these tumors. Therefore, the discovery of this novel genomic signature can be used for prognostication of lung cancer patients, and most importantly we can tailor personalized novel immunotherapies for their treatment.

Abstract

Lung cancer is one of the leading causes of death worldwide. Cell death pathways such as autophagy, apoptosis, and necrosis can provide useful clinical and immunological insights that can assist in the design of personalized therapeutics. In this study, variations in the expression of genes involved in cell death pathways and resulting infiltration of immune cells were explored in lung adenocarcinoma (The Cancer Genome Atlas: TCGA, lung adenocarcinoma (LUAD), 510 patients). Firstly, genes involved in autophagy (n = 34 genes), apoptosis (n = 66 genes), and necrosis (n = 32 genes) were analyzed to assess the prognostic significance in lung cancer. The significant genes were used to develop the cell death index (CDI) of 21 genes which clustered patients based on high risk (high CDI) and low risk (low CDI). The survival analysis using the Kaplan–Meier curve differentiated patients based on overall survival (40.4 months vs. 76.2 months), progression-free survival (26.2 months vs. 48.6 months), and disease-free survival (62.2 months vs. 158.2 months) (Log-rank test, p < 0.01). Cox proportional hazard model significantly associated patients in high CDI group with a higher risk of mortality (Hazard Ratio: H.R 1.75, 95% CI: 1.28–2.45, p < 0.001). Differential gene expression analysis using principal component analysis (PCA) identified genes with the highest fold change forming distinct clusters. To analyze the immune parameters in two risk groups, cytokines expression (n = 265 genes) analysis revealed the highest association of IL-15RA and IL 15 (> 1.5-fold, p < 0.01) with the high-risk group. The microenvironment cell-population (MCP)-counter algorithm identified the higher infiltration of CD8+ T cells, macrophages, and lower infiltration of neutrophils with the high-risk group. Interestingly, this group also showed a higher expression of immune checkpoint molecules CD-274 (PD-L1), CTLA-4, and T cell exhaustion genes (HAVCR2, TIGIT, LAG3, PDCD1, CXCL13, and LYN) (p < 0.01). Furthermore, functional enrichment analysis identified significant perturbations in immune pathways in the higher risk group. This study highlights the presence of an immunocompromised microenvironment indicated by the higher infiltration of cytotoxic T cells along with the presence of checkpoint molecules and T cell exhaustion genes. These patients at higher risk might be more suitable to benefit from PD-L1 blockade or other checkpoint blockade immunotherapies.

Multifocal Necrotizing Leukoencephalopathy: Expanding the Clinicopathologic Spectrum

Multifocal necrotizing leukoencephalopathy (MNL) is a rare condition typically described in patients undergoing chemotherapy or with HIV/AIDS. As a pathologic entity, it is characterized by multiple small foci of necrosis typically within white matter of the pons and occasionally in other areas. Herein we describe findings in 6 patients with MNL, 5 diagnosed at postmortem examination and 1 by surgical biopsy. Histopathologic features were characteristic, with generally small foci of necrosis, most frequently within the pontine base, although larger lesions were seen in the frontal white matter and basal ganglia. Axonal swellings, occasional dystrophic calcification and minimal microglial activity or reactive responses were common. Glial fibrillary acidic protein immunoreactivity was absent or markedly reduced within the lesions although it remained well defined in the surrounding areas. The underlying clinical circumstances ranged from HIV/AIDS, hematologic malignancy, chemotherapy for malignancies to postcardiac transplant, the latter reported for the first time. A significant common thread identified in our cases was altered immune status. A second common factor, which has also been previously implicated, was the presence of significant ongoing infection or sepsis. The role of concurrent inflammatory processes, specifically proinflammatory cytokine release in the context of these complex clinical scenarios is discussed with possible pathogenetic considerations.

Abstract 1974: Autocrine TIMP-1-mediated chemoresistance via induction of IL-6 in NSCLC

Our previous studies have confirmed the well-defined antiapoptotic functions of TIMP-1. We have shown that overexpressing TIMP-1 in NSCLC cells increases cell survival with activation of the ERK pathway via phosphorylation of BAD at serine 112. Knocking down TIMP-1 in NSCLC cells increased the levels of miR-125a-5p with concomitant upregulation in apoptosis. These studies beg the question- does modulation of TIMP-1 affect chemotherapy in NSCLC? To address this question we examined two cell lines, A549 and H460, and their specific shRNA-mediated TIMP-1 gene knockdown clones. We found that TIMP-1 mediated chemoresistance against two front line chemotherapeutic agents (Gemcitabine and Cisplatin) as determined by increased apoptosis in the KD clones. In order to determine any contribution of cytokine activity towards this antiapoptotic function of TIMP-1, we carried out a cytometric bead array assay. The results of this screening assay which included potential inflammatory cytokines and growth factors, indicated that IL-6 plays a role in mediating the chemoresistance in TIMP-1 expressing NSCLCs. We then determined endogenous IL-6 levels in our array of NSCLC cell lines and found a direct correlation of IL-6 levels with TIMP-1 levels. It is important to note that IL-6 expression is precisely regulated with TIMP-1 production at both protein and mRNA levels. The effect of TIMP-1 on IL-6 levels is more pronounced under hypoxic versus normoxic conditions. Importantly, IL-6 expression is upregulated by addition of exogenous human recombinant TIMP-1 in a time- and dose- dependent manner. Blocking of TIMP-1 signaling with specific neutralizing antibodies delayed the IL-6 upregulation. Moreover, addition of rhTIMP-1 or rhIL-6 rescued apoptosis induced by chemotherapeutic agents albeit to a limited extent. Although early in the investigation, our studies suggest that interventions impacting the TIMP-1/IL-6 axis in NSCLCs may provide an efficient target to boost effects of clinical chemotherapy.

Citation Format: Wei Xiao, Amyn M. Rojiani, Sampa Ghoshal Gupta, Mumtaz V. Rojiani. Autocrine TIMP-1-mediated chemoresistance via induction of IL-6 in NSCLC [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 1974.

TIMP-1 downregulation modulates miR-125a-5p expression and triggers the apoptotic pathway

Matrix metalloproteinases and their natural inhibitors (TIMPs) are important elements in a wide range of oncology settings. Elevated levels of tissue inhibitor of metalloproteinase-1 (TIMP-1) have often been associated with increased tumorigenesis. This has been demonstrated in a number of clinical and experimental models which include breast, gastric, colorectal and non-small cell lung carcinoma (NSCLC). Our earlier studies have identified increased angiogenic activity and aggressive tumor kinetics in TIMP-1 overexpressing H2009 lung adenocarcinoma cells. TIMP-1 overexpression has also been implicated in antiapoptotic responses, inducing a significant upregulation of Bcl-2. These TIMP-1 functions have been shown to be MMP-independent and provide insight into its pleiotropic activities. The current study examines microRNA (miRNA) interactions with this molecule. We have sought to define the relationship between TIMP-1 and miRNA by knocking down TIMP-1 in high TIMP-1 expressing lung adenocarcinoma cell lines. TIMP-1 knockdown resulted in increased expression of miR-125a-5p with a concomitant increase in apoptosis and attenuation of the tumorigenic features of these cells. We have identified TIMP-1 as a bona fide target of miR-125a-5p, and their interaction resulted in an increase in p53 expression. We further corroborated our in vitro data with patient samples, which exhibited an inverse correlation between TIMP-1 and miR-125a-5p expression. Our study lends support to the notion that elevated TIMP-1 levels, which are frequently associated with poor prognosis, cause aberrant modulation of miRNAs.

Morphologic and Elemental Analysis of Primary Melanosis of the Dentate Nucleus: Review and Correlation With Neuromelanin

Primary melanosis of the dentate nucleus is a rarely described entity with neither known cause nor definitive clinicopathologic correlation. We revisit this previously reported phenomenon by presenting one such case with a review of the pathology as well as additional investigations including elemental analysis by energy-dispersive X-ray, immunohistochemistry and electron microscopy. The lesion presented macroscopically as a sharply defined, black pigmentation that was restricted to the dentate nucleus of the cerebellum. Other deep nuclei were uninvolved. Similarly, other areas of the cerebellum, brainstem, and supratentorial regions were macroscopically free of pigment. Microscopically, however, the pigment was noted to be present, albeit in microscopic deposits, within layers of the cerebellar cortex. Additionally, immunohistochemistry and electron microscopy defined an intracellular component within astrocytes. X-ray analysis of the pigment showed it to consist almost entirely of sulfur, an element known to be prominent in neuromelanin. This report also describes an association of the pigment with astrocytes by ultrastructural examination. We discuss the results of our findings in the context of etiopathogenetic considerations, seeking to gain a better understanding of this abnormal pigmentation and its relationship to neuromelanin.

Abstract 5906: TIMP-1 expression is inversely correlated with miRNA125a-5p and let-7e in non-small-cell lung carcinoma

Epigenetic alterations are emerging as significant elements in our understanding the biology of lung cancer which remains the leading cause of cancer deaths worldwide. In earlier studies we have shown that tissue inhibitor of metalloproteinase 1 (TIMP-1) overexpression in NSCLC cells results in aggressive tumors in mice. We have also demonstrated TIMP-1’s anti-apoptotic activity in these cells. It is well documented that miRNAs are involved in many physiological and neoplastic processes, including apoptosis. We have previously shown that knocking down TIMP-1 in A549 NSCLC cells alters the miRNA profile in these cells with upregulation of miR-125a-5p. Subsequently, we have identified that miR let-7e is also upregulated in TIMP-1 KD clones. The present study is focused on confirming the involvement of miR-125a-5p with TIMP-1 by using mimics and antagomirs of 125a-5p. Furthermore, we have sought to validate this relationship in vivo by examining these patterns in clinical samples. We added mimics of miR-125a-5p into the parental A549 cells, which resulted in down regulation of TIMP-1 levels. We were then able to rescue TIMP-1 downregulation by adding antagomirs of miR-125a-5p to the same cells. MiR-125a-5p binding sites were identified in TIMP-1 3’ UTR and using luciferase assay, we have confirmed that TIMP-1 is indeed a bona fide target of miR-125a-5p. Translational studies were carried out using archived NSCLC adenocarcinoma tissues from the Surgical Pathology archives at AU Medical Center. We first measured expression level of TIMP-1 by RT-PCR in 20 tumors and paired normal adjacent tissues and divided the samples into 2 groups, those with low and high TIMP-1 expression levels. Tissues were then interrogated for TIMP-1 and miR-125a-5p and let- 7e miRNA expression using chromogenic in situ hybridization. We identified negative correlation pattern between tumor and paired normal adjacent tissue samples. Generally, TIMP-1 was highly expressed in the tumor region, while miRNA expression was relatively decreased when compared with adjacent normal tissues. miRNA 125a-5p and let- 7e are known tumor suppressors in NSCLC. Analyzing secondary data (adenocarcinoma) by KM plotter we found that high TIMP1 correlated with lower patient survival with a hazard ratio of 3.17 (2.3-4.37) and a log rank p value of 8.1e-14. These studies provide additional clarity and further extend our understanding of the relationship between these miRNA families and TIMP-1 expression.

Citation Format: Ammar Kutiyanawalla, Sampa Ghoshal-Gupta, Byung R. Lee, Ashis Mondal, Ravindra Kolhe, Amyn M. Rojiani, Mumtaz V. Rojiani. TIMP-1 expression is inversely correlated with miRNA125a-5p and let-7e in non-small-cell lung carcinoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 5906. doi:10.1158/1538-7445.AM2017-5906

Vessel morphometric parameters-correlation with histologic grade and VEGF expression in oligodendroglioma

The contributions of histologic features including microvascular proliferation to the determination of malignancy in oligodendrogliomas remain uncertain. We have retrospectively performed morphometric assessments in 20 tumors histologically classified as well-differentiated (WHO Grade II, n=8) or anaplastic (WHO Grade III, n=12) oligodendrogliomas (WDO or AO). Quantitative studies utilized image analysis of double immunolabeled vasculature with anti CD34 with VIP chromogen (purple) and proliferating nuclei with anti MIB-1, using DAB (brown). Mean values are reported from five fields for each of twenty cases. The total number of MIB-1 positive tumor nuclei was 10 fold higher in AO vs WDO. The area occupied by vessels was also markedly increased in AO vs WDO, as was the microvessel density. Proliferating endothelial cells i.e. those with MIB-1 positive nuclei in CD34 positive cells were significantly increased (4.6 vs 0.26 positive nuclei per unit tumor area, P≤0.001) in AO. While in most areas these changes were evident as typical microvascular proliferation, other areas showed thin walled vessels with increased MIB-1 positivity. VEGF was only assessed morphologically and showed positive staining of vasculature only, in WDO, while AO also showed immunoreactivity of vessels and multiple areas of tumor cells. These findings support a contributory role for vascular proliferation in assessing histologic grade. These findings also suggest that VEGF expression which is confined to blood vessels in lower grade tumors but eventually is expressed by tumor cells in higher grade oligodendrogliomas may be an important factor as the tumor progresses.

Abstract 3368: TIMP-1 and angiogenesis: A role for CDH5 and eNOS

Tissue inhibitors of metalloproteinases (TIMP) have emerged as diverse molecules with novel roles in apoptosis, angiogenesis and metastasis. TIMP-1, a well-documented inhibitor of apoptosis, has been shown to inhibit or promote angiogenesis. In recent years, a strong association has also been demonstrated between high levels of TIMP-1 and poor prognosis in many cancers. It has been recognized as a multifunctional protein affecting cell growth and angiogenesis. Conflicting studies have shown it to function either as a negative or a positive regulator of angiogenesis. In earlier studies, we have documented that lung adenocarcinoma cell line H2009, when transfected to overexpress TIMP-1 and injected into nude mice resulted in larger, more aggressive tumors with increased microvessel density, which was supported by in vitro angiogenesis assays whereby enhanced capillary network formation was seen. We have also shown that TIMP-1 expression levels can be correlated with KRAS independency in non-small-cell lung carcinoma (NSCLC) cell lines harboring KRAS mutations. The present study was undertaken to address the role of TIMP-1 in angiogenesis in the context of KRAS in NSCLC cell lines. KRAS dependent cell line H2009 and its TIMP-1 overexpressing clone HB1 and a KRAS independent cell line A549 and its TIMP-1 knockdown (KD) clone SH3 were examined by angiogenesis specific PCR array. Comparison of the angiogenesis associated profiles of these cell lines identified a marked increase in vascular endothelial cadherin CDH5 in TIMP-1 over-expressing clone HB1. KRAS independent A549 cells expressed high level of CDH5, however its TIMP-1 KD clone exhibited a marked decrease in CDH5 level. A similar profile was identified for endothelial nitric oxide synthase (eNOS/NOS3). CDH5 is an indispensable element of normal vascular development and maintenance, and any perturbations of normal levels will impact vessel sprouting and growth. eNOS is primarily active through production of nitric oxide, maintaining vascular tone as well as expressing anti-proliferative and antithrombotic properties. We confirmed our earlier observation that serum free conditioned media (SFCM) from TIMP-1 overexpressing HBI cells caused increased and more complex network formation. SFCM from A549 TIMP-1 KD SH3 clone showed a marked inhibition of endothelial network formation compared to SFCM from A549 cells. To confirm that TIMP-1 was responsible for the changes observed we purified secretory TIMP-1 by combined fast protein liquid chromatography and gel filtration from another high TIMP-1 producing NSCLC cell line (H460) and also observed more capillary network formation in human umbilical vein endothelial cells. Our studies suggest that TIMP-1 modulates angiogenesis by impacting CDH5 and eNOS positively. These results define an important function of TIMP-1 in angiogenesis and provide additional therapeutic targets for managing NSCLC.

Citation Format: Sampa Ghoshal-Gupta, Ian A. Coe, Ammar Kutiyanawalla, Byung R. Lee, Amyn M. Rojiani, Mumtaz V. Rojiani. TIMP-1 and angiogenesis: A role for CDH5 and eNOS. [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 3368.

Abstract 5073: Role of TIMP-1 glycosylation in lung carcinoma

Tissue inhibitors of matrix metalloproteinases (TIMPs) were initially identified as endogenous physiological inhibitors of MMPs. However, over recent years novel functions have been attributed to TIMPs, especially TIMP-1. Amongst its complex and sometimes paradoxical functions,TIMP-1's role in inhibition of apoptosis and cell proliferation is well-documented. Our initial studies have shown that overexpressing TIMP-1 in a lung adenocarcinoma cells results in larger and more aggressive tumors when implanted in the mouse brain. This has also been corroborated in vitro, by demonstrating increased invasion and anchorage-independent growth as well as decreased apoptosis.

In the present study, we have purified human TIMP-1 in order to examine its direct molecular activity in tumorigenesis. Non-small cell lung carcinoma cell line NCI-H460 was utilized because it normally produces high levels of TIMP-1 as confirmed by western blot analysis and ELISA. We found that TIMP-1 was secreted directly into the culture media and we could not identify presence of TIMP-1 in the exosome fraction. TIMP-1 was purified from serum-free conditioned media of NCI-H460 by ammonium precipitation, ion exchange chromatography followed by gel filtration, with resultant purity of greater than 90%. The addition of purified exogenous TIMP-1 to NCI-H2009, a low TIMP-1 producing NSCLC cell line, resulted in increased cell proliferation and reduced cytotoxicity from environmental stressors such as air exposure, H2O2, staurosporine and cycloheximide as determined by LDH assay. Flow cytometric analysis following addition of purified TIMP-1 to H2009 cells demonstrated reduced apoptosis. A549, a lung adenocarcinoma cell line that produces levels of TIMP-1, higher than H2009, was found to be relatively insensitive to exogenously added purified TIMP-1. This may be interpreted as indicating concentration dependent activity of TIMP-1. Deglycosylated TIMP-1 (by PNGase F treatment) as well as recombinant human TIMP-1 (from E.coli) did not exhibit any protective functions indicating that glycosylation is critical for the cell proliferative and anti-apoptotic functions of TIMP-1. To investigate whether the protective function of TIMP-1 is MMP-dependent, we constructed a T2G mutant of TIMP-1 where changing the second amino acid threonine to glycine resulted in impaired MMP-inhibition function. The T2G mutant was also as protective of cell survival as TIMP-1, supporting the concept that this is an MMP-independent function. Collectively our results indicate that TIMP-1 glycosylation is critical for exogenous TIMP-1 to induce cell proliferation and cell survival in an MMP-independent manner, most likely through receptors that recognize glycosylated TIMP-1. This study was supported in part by a Distinguished Cancer Scientist Award to AMR from the Georgia Research Alliance.

Citation Format: Byung R. Lee, Ammar Kutiyanawalla, Sampa Ghosal-Gupta, Amyn M. Rojiani, Mumtaz V. Rojiani. Role of TIMP-1 glycosylation in lung carcinoma. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 5073. doi:10.1158/1538-7445.AM2015-5073

Abstract A49: Biological impact of TIMP-1 relative to KRAS status in lung carcinoma

Comprehensive sequence analysis of common human cancers has identified several genes that promote tumorigenesis. KRAS is a commonly mutated oncogene in lung adenocarcinoma, most frequently harboring mutations in codon 12 or 13. Therapeutically targeting of KRAS with small molecules has proven ineffective due to difficulties in disrupting protein/protein interactions that are inherent in its activation and function. Recent work has established that many cancers may have KRAS addiction and are considered KRAS dependent while others do not require KRAS for survival. Previously we have shown that TIMP-1 plays an important role in cell survival in lung adenocarcinoma cells. We have overexpressed TIMP-1 in H2009, a KRAS dependent cell line, which rendered these cells resistant to Staurosporine induced apoptosis, whereas knocking down TIMP-1 in A549 (a KRAS independent lung carcinoma cell line) had the opposite effect. We also noted that TIMP-1 overexpression in H2009 cells made them more angiogenic and aggressive in in vitro assays. H2009 and A549 cell lines also showed significant differences in migration, spheroid formation as well as invasiveness. Although H441 cell line is known to be KRAS dependent, it was not as invasive as H2009. These cell lines also showed differential expression of Vimentin and E-cadherin. These results prompted us to review available data regarding these cell lines, which not only harbored different mutations in the cancer promoting genes, but also differed at the regulatory level and functioned through activated ERK1/2, NFkB and Akt pathways. Analysis with the R2 program (http://hgserver1.amc.nl/cgi-bin/r2/) identified a significant correlation between TIMP-1 and KRAS in breast cancers and lung cancer . Interestingly, high TIMP1 levels have been shown to cause chemoresistance by virtue of its anti-apoptotic activity and KRAS has generally been undruggable. Our current study compares KRAS dependent and independent cell lines in relation to TIMP-1 expression. Modulating TIMP-1 renders these cells either more sensitive or resistant to apoptosis. Clinically, patients with elevated TIMP-1 expression have been shown to have shorter overall survival. This study helps to further dissect these pathways and provides a better understanding of the impact of these mutations in lung carcinoma. Supported in part by a Georgia Research Alliance Distinguished Cancer Scientist Award.

Citation Format: Sampa Ghoshal Gupta, Ammar Kutiyanawalla, Byung Rho Lee, Amyn M. Rojiani, Mumtaz V. Rojiani. Biological impact of TIMP-1 relative to KRAS status in lung carcinoma. [abstract]. In: Proceedings of the AACR Special Conference on RAS Oncogenes: From Biology to Therapy; Feb 24-27, 2014; Lake Buena Vista, FL. Philadelphia (PA): AACR; Mol Cancer Res 2014;12(12 Suppl):Abstract nr A49. doi: 10.1158/1557-3125.RASONC14-A49

Abstract 5269: Impact of K-ras status on differential expression of TIMP-1 in lung adenocarcinoma

Tissue inhibitor of metalloproteinase-1 exhibits a range of novel functions in addition to its initially recognized activity as a physiological inhibitor of MMPs. Two specific activities have been of significant interest in the context of oncology - inhibition of apoptosis and induction of cell proliferation. Previously we have shown that over-expressing TIMP-1 in a lung adenocarcinoma cell line H2009 results in more aggressive and larger tumors in vivo with increased invasion and colony formation in vitro. Subsequently we demonstrated elevated levels of Bcl-2 with a concomitant reduction in apoptosis induced by staurosporine. In the present study, we have sought to define a relationship between TIMP-1 expression levels in non-small-cell-lung-carcinoma (NSCLC) cell lines in relation to K-ras mutation. We identified a differential expression pattern of TIMP-1 in various NSCLC cell lines and also found that TIMP-1 overexpressing cell lines also had higher levels of Bcl-2 and vice versa. Upon further analysis, we were able to correlate a low TIMP-1 expression with K-ras dependence and high levels of E-cadherin expression as in H2009 and H441. Similarly, K-ras independent cell line A549, expressed low levels of E-cadherin and elevated TIMP-1. E-cadherin distribution was confirmed in A549 and H2009 cells by immunofluorescence. Since N-cadherin cleavage has been shown to be inhibited by TIMP-1, we examined N-cadherin levels by western blot. Results indicate that A549 exhibiting high levels of TIMP-1 had increased levels of N-cadherin whereas the low TIMP-1 expressing cell lines had lower N-cadherin levels. A spheroid formation assay to determine the aggressiveness of cell lines revealed that K-ras dependent cell line formed spheroids that were smaller and less migratory than K-ras independent cell line whereas the K-ras independent cell line A549 formed spheroids that were larger, more spread out exhibiting wider migratory properties. The present study underscores the multiple biologic properties of TIMP-1. It provides further mechanistic understanding of its documented role as a prognostic marker and a potential therapeutic target in various malignancies, particularly lung carcinoma. This study was supported in part by a Distinguished Cancer Scientist Award to AMR from the Georgia Research Alliance.

Citation Format: Ammar Kutiyanawalla, Sampa Gupta-Ghoshal, Byung Rho Lee, Ravindra Kolhe, Amyn M. Rojiani, Mumtaz V. Rojiani. Impact of K-ras status on differential expression of TIMP-1 in lung adenocarcinoma. [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 5269. doi:10.1158/1538-7445.AM2014-5269

Vascular alterations in schwannoma

Schwannomas or neurilemmoma are benign peripheral nerve sheath tumors, which most frequently occur at the cerebellopontine angle. This morphologic study examines vascular alterations in these tumors, comparing them to other benign spindle cell neoplasms of the nervous system, while correlating these findings with evidence of vascular permeability. Thirty-four nervous system spindle cell neoplasms, sixteen schwannomas, nine fibroblastic/transitional meningiomas and nine peripheral neurofibromas were stained with H&E, Prussian-blue stain, and immunoreacted for factor VIII-related antigen and interstitial albumin. Schwannomas had focal clusters of vascular proliferation including groups of small thin-walled vessels, as well as larger vessels with extensive hyalinization. Neurofibromas and meningiomas almost uniformly had modest numbers of well-defined, thin walled individual vessels. Free hemosiderin and hemosiderin-laden macrophages were frequently identified in schwannomas. Prussian-blue stain for iron revealed focal or fairly widespread positivity in almost all schwannomas, only one meningioma and none of the neurofibromas. Immunoreaction for albumin demonstrated leakage of vascular proteins into the interstitium confirming tumor vessel permeability in schwannomas. Neither neurofibromas nor meningiomas displayed any detectable interstitial albumin. The above findings confirm a degree of reactive proliferation of vessels in schwannoma along with functional deficits in their vascular integrity with permeability to protein and blood. The presence of hyalinized vessels, hemosiderin, both free and within macrophages, and more readily evident Prussian blue staining, may provide an additional diagnostic clue in discriminating between histologically similar spindle cell lesions. The study however raises the possibility that these changes likely precede or facilitate the degenerative 'ancient change' seen in some schwannoma.

Abstract 3086: Modulation of microRNA profile in lung adenocarcinoma cell line following TIMP-1 downregulation

Non-small cell carcinoma accounts for 85% of lung cancer cases and has a 5 year survival rate of only 17%. In recent years, tissue inhibitor of metalloproteinase-1 (TIMP-1) has emerged as an important prognostic marker. In several cancers including non-small cell lung cancer, high serum levels of TIMP-1 have been associated with poor prognosis. Previously, we have shown that overexpressing TIMP-1 in H2009, a lung adenocarcinoma cell line resulted in aggressive tumors when implanted in the mouse brain. In the present study, we have knocked down TIMP-1 expression in the non-small cell lung cancer cell line A549 using shRNA. In vitro assays using the TIMP-1 knockdown clones defined decreased migration in wound assays (p&lt;0.01), as well as reduced invasion (p&lt;0.05) using Boyden chamber assays. We investigated these functional alterations by examining microRNAs in these cell lines. MicroRNAs represent a class of small non-coding RNAs that regulate gene expression at the post-transcriptional level and control crucial signaling and physiological processes functioning either as oncogenes or tumor-suppressors. The miRNA expression profile of A549 cell line and its TIMP1 knockdown clone were evaluated using the Affymetrix miRNA microarray platform on Gene-Chip miRNA 3.0 array in A549 cell line. Following hybridization and data acquisition, we used Partek Genomics Suite ® software for RNA normalization and to determine statistically significant differences in miRNA expression between experimental groups by ANOVA and pairwise comparisons (two-sidedα=0.05). Using the Affymetrix miRNA array we have identified altered miRNAs expression in the clones, with 72 differentially regulated miRNAs following TIMP-1 knockdown. Using quantitative real time PCR we have selectively validated several of the miRNAs that showed the maximal difference. We have confirmed a 2 to 4-fold down regulation of MiR-10b, miR-29a and miR-30 and a 3-fold upregulation of miR-125a-5p. Based on KEGG pathway analysis, this group of validated miRNAs are involved in the MAPK signaling pathway. Western blot analysis showed activation of the apoptosis inducing p38 MAPK pathway in the knockdown clones. Additional mechanistic dissection of these changes and involved pathways will contribute further to our understanding of the role of TIMP-1 in lung cancer. (This research was supported by a Georgia Distinguished Cancer Scholar award to AMR).

Citation Format: Sampa Ghoshal-Gupta, Ammar Kutiyanawalla, Shahanawaz Jiwani, Juhi Ojha, Ravindra Kolhe, Amyn M. Rojiani, Mumtaz V. Rojiani. Modulation of microRNA profile in lung adenocarcinoma cell line following TIMP-1 downregulation. [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 3086. doi:10.1158/1538-7445.AM2013-3086

Abstract 4955: TIMP-1 inhibits apoptosis in lung adenocarcinoma cells via Bcl-2 interaction

Tissue inhibitors of matrix metalloproteinases have multifunctional properties, orchestrating diverse biological activities. Previous studies revealed a novel function of TIMP-1 as an inhibitor of apoptosis in mammalian cells. However, the mechanisms by which TIMP-1 exerts its anti-apoptotic effect are not completely understood. The antiapoptotic effect has been correlated with higher levels of Bcl-Xl. Our earlier studies in a CNS model of metastasis, using HB-1, a TIMP-1 overexpressing lung adenocarcinoma cell line (H2009), resulted in more aggressive tumor kinetics and increased vasculature. The present study was undertaken to elucidate the role of TIMP-1 in apoptosis in our model. Utilizing an apoptosis -specific gene array, we found that TIMP-1 overexpression results in 3-fold increased expression of Bcl-2. H2009 and the TIMP1 over-expressing clone - HB1 were treated with staurosporine to induce apoptosis, followed by analysis for poly ADP-ribose polymerase (PARP) cleavage. HB1 showed marked reduction in PARP cleavage in comparison to the controls. Treatment of HB1 cells with ABT737, an inhibitor of Bcl-2, restored apoptosis resulting in PARP cleavage in this clone. To further confirm this mechanism, we induced transient inhibition of Bcl-2 with siRNA, which also restored PARP cleavage in the HB-1 clone. Thus both chemical and biological inhibition resulted in increased apoptosis. Additionally, immunoprecipitation of Bcl-2 from cell lysate co-immunoprecipitated TIMP-1 suggesting a direct interaction between TIMP-1 and Bcl-2. These investigations identify a relationship between TIMP-1 and Bcl-2 in apoptosis inhibition, contributing to aggressive tumor kinetics, utilizing non-MMP dependent mechanisms.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 4955. doi:1538-7445.AM2012-4955

Abstract 5294: Increased angiogenesis resulting from TIMP-1 inhibition of TSP-1 is mediated by PI3kinase and FAK interactions

Tissue Inhibitor of Matrix Metalloprotease -1 (TIMP-1), one of the four natural inhibitors of matrix metalloproteinases was initially identified for its Erythroid Potentiating Activity. Since then, it has been shown to independently induce cell proliferation and inhibit apoptosis in a number of cell types. TIMP-1 has also been shown to promote, but also more often to inhibit angiogenesis. Previously, we have shown that TIMP-1 overexpression in a lung adenocarcinoma cell line (H2009) resulted in more aggressive and vascular tumors in nude mice and increased capillary network formation and tumorigenicity in vitro. An angiogenesis pathway-specific gene array had identified a 3-fold reduction in thrombospondin 1 (TSP-1) levels in the TIMP-1 overexpressing clone HB-1. TSP-1 siRNA clone exhibited a similar increase in in vitro angiogenesis assays. In the present study, we have sought to identify the signaling pathway involved whereby TIMP-1 inhibits TSP-1. To this end, we have used specific inhibitors to inhibit TIMP1 initiated signaling pathways. MAP kinase, PI3/Akt inhibitors were used, either singly or in combination with Focal Adhesion kinase (FAK) inhibitor. Our results indicate a synergistic interaction between PI3/Akt pathway and FAK signaling, which restores TSP-1 levels by approximately 3-fold relative to control. Gelatin zymography of serum-free conditioned media (SFCM) revealed a reduction in proMMP-9 level in the HB-1 clone versus H2009. Additionally MMP9 specific ELISA reveals a two-fold reduction in MMP9 levels. This is in tune with the role of TSP-1 as an inhibitor of MMP-9 activation such that decreased TSP-1 level results in increased activation of MMP-9 with a concomitant reduction in the extracellular level of proMMP-9. Thus our findings define interaction of TIMP-1 via PI3kinase and FAK signaling. resulting in TSP-1 decrease and subsequent downstream promotion of angiogenesis with increased tumor kinetics.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 5294. doi:1538-7445.AM2012-5294

Expression of MMP-2 correlates with increased angiogenesis in CNS metastasis of lung carcinoma

Matrix metalloproteinases (MMP) have been implicated in increased invasive and metastatic potential of tumors, possibly via interactions with the extracellular matrix and angiogenesis. This study investigates the relationship between MMP-2 immunoexpression and angiogenesis in a series of lung carcinomas metastatic to the central nervous system (CNS). Twenty eight metastatic carcinoma cases with adequate brain-tumor interface were identified from the archives at the Moffitt Cancer Center. MMP-2 expression was determined by immunohistochemistry using an antibody directed against pro and active forms (NeoMarkers). Similarly, microvessels were identified on parallel sections with anti-CD34 antibody (Biogenix). Angiogenesis profiles within the tumor and at the CNS/tumor interface were morphometrically assessed by the Image Pro Plus image analysis system. Briefly, CD34 positive vessels were quantitated and correlated with presence or absence of MMP-2 expression in the tumor. Mean microvessel area (MMVA) and mean microvessel number (MMVN) were assessed within areas of brain-tumor interface and within the tumor and expressed as a ratio relative to the tumor. Sixteen (57.14%) metastatic tumors were strongly immunoreac-tive for MMP-2, while 12 (42.86%) were negative. MMP-2 positive tumors had a higher MMVA and MMVN ratio at the CNS/tumor interface in comparison to MMP-2 negative neoplasms. MMP-2 expression thus appears to confer enhanced vascular proliferation particularly at the brain-tumor interface which would support the contention of enhanced capability of growth and invasion within the CNS, possibly modulated by MMP2. The relationship between MMP-2 expression and angiogenesis has been previously reported and its biological and therapeutic implications remain the focus of investigations.

CD44 and p53 immunoexpression patterns in NF1 neoplasms - indicators of malignancy and infiltration

Neurofibromatosis type 1 (NF1) provides a unique system to evaluate the complete range of neoplastic expressions, from encapsulated benignity to invasiveness and malignancy. This study was aimed at determining whether CD44 and p53 may serve as indicators of malignant progression of neurofibroma. CD44, a transmembrane glycoprotein receptor for hyaluronic acid, and participates in cell-extracellular matrix interactions and migration. CD44 may play a vital role, either through under or overexpression, with invasion and metastases of tumors, altering their ability to infiltrate the adjacent tissue. The tumor suppressor gene, p53, has also been implicated in malignant progression of various human tumors including malignant peripheral nerve sheath tumors (MPNST). A total of 44 tumors from 33 patients with NF1 were evaluated with an anti-human CD44H, CD44 splice variant v6 and anti-p53 monoclonal antibodies. Morphologic expression patterns of expression were evaluated for CD44 while semiquantitative criteria were applied to assess, p53 nuclear positivity. Immunoexpression of p53 was markedly higher in 12 of 16 MPNST (75%). Thirteen of 28 (46%) benign neurofibroma also had some expression of p53 above 'normal level', although much lower than the MPNST. Plexiform neurofibroma did not differ from other benign lesions in their expression of p53. Our results suggest that p53 mutation as evidenced by immunohistochemical overexpression is a factor in malignant transformation and progression of neurofibroma. 70% of benign neurofibroma demonstrated some, usually focal, CD44 positivity. The pattern of CD44 expression in plexiform neurofibroma was revealing, as it was maximal in the 'nonencapsulated' portions of the tumors. Eight of 11 (72%) locally infiltrative cutaneous neurofibroma and 13 of 16 (81%) MPNST exhibited diffuse CD44 positivity. CD44v6 expression was positive in control tissues but was not identified in any of tumor samples. Also, within the confines of encapsulated tumors CD44 expression is limited, while in poorly circumscribed neurofibroma CD44 expression is upregulated. This is interpreted as a reflection of the interaction of CD44+ tumor cells with extracellular matrix, hence facilitating infiltrative behavior.

Abstract 3444: The role of p75ntr and TIMP-1 in U251 malignant glioma cells

The neurotrophin receptor p75NTR and trk receptors play an important role in the diverse functions of neurotrophins in the CNS. These include survival, differentiation, neurite outgrowth and development in the nervous system. More recently, an emerging role for the p75NTR has been described in tumor biology, both within the nervous system as well as in non-nervous system neoplasms. Investigative studies in vitro and in vivo have identified both tumor promoting and tumor inhibitory functions of p75NTR, related to specific tumor types. p75NTR has been implicated as a tumor and metastasis suppressor gene and in promoting apoptosis, particularly within the prostate. It has been suggested that p75NTR interactions in the microenvironment result in decreasing MMP2 and MMP9, with a concomitant increase in TIMP1 expression. These have a negative effect on tumor kinetics. However, these tumor promoting and tumor inhibitory functions of p75NTR have been reported in context of specific tumor types. Previously, we have shown that over-expressing TIMP1 in H2009, a lung adenocarcinoma cell line resulted in decreased expression of p75NTR in the clone HB1 compared to H2009. This clone was found to be more aggressive in both in vitro and in vivo studies. Extending these studies to glial neoplasms we sought to define a role of TIMP1in the modulation of p75NTR activities. To this end, we over-expressed TIMP1 in U251 glioma cell line. The resulting stable clones expressed decreased levels of p75 RNA and again behaved more aggressively in vitro with increased tumorigenicity and angiogenesis as evidenced by enhanced colony formation in soft agar as well as increased capillary network formation on Matrigel when serum-free conditioned media was used from the clone compared to parental U251 cell line. We have utilized p75 siRNA to knockdown the levels of p75NTR in U251 glioma cell line. Stable clones expressing reduced levels of p75 showed an increase in the number as well as the size of colonies in soft agar assay compared to the parental cell line suggesting increased tumorigenicity. Collectively our studies appear to define a tumor suppressor function for p75NTR. Additional studies are ongoing to further define the role of p75NTR and TIMP1.

Note: This abstract was not presented at the AACR 101st Annual Meeting 2010 because the presenter was unable to attend.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 3444.

In vitro interaction of a polypeptide homologous to human Ro/SS-A antigen (calreticulin) with a highly conserved amino acid sequence in the cytoplasmic domain of integrin alpha subunits

We endeavored to identify proteins interacting with KLGFFKR, a highly conserved motif in the cytoplasmic domain adjacent to the transmembrane domain of the alpha subunit of integrins. We found that affinity chromatography of cell extracts with this peptide followed by elution with EDTA resulted in the isolation of a 60-kDa protein (p60). The N-terminal amino acid sequence of this 60-kDa polypeptide was found to be highly homologous to the Ro/SS-A antigen, a 60-kDa protein homologous to calreticulin and Aplysia "memory molecule". The binding of p60 was found to be specific for the KLGFFKR sequence since this polypeptide did not bind to a peptide with a scrambled amino acid sequence (KLRFGFK), and it was also specifically eluted from the KLGFFKR affinity matrix ith soluble KLGFFKR peptide but not with the scrambled peptide. Solid phase in vitro binding assays demonstrated specific interaction of p60 with integrin alpha 3 and alpha 5 subunits but not with the beta 1 subunit. Furthermore, p60 could be copurified with alpha 3 beta 1 following coincubation in vitro. These interactions could be inhibited by KLGFFKR peptide and also by EDTA, indicating sequence-specific and divalent cation dependent binding. Despite the fact that calreticulin is thought to be localized in the endoplasmic reticulum, a pool of Ro/SS A antigen homologous 60-kDa polypeptide was found to be present in the soluble cytoplasm, indicating the feasibility of an interaction of p60 with the integrin alpha subunits. Our data suggest that p60 (Ro/SS-A Ag) can specifically bind to integrin alpha subunits via the highly conserved KLGFFKR amino acid sequence.

Relationship between protein synthesis and concentrations of charged and uncharged tRNATrp in Escherichia coli

We have continuously monitored Trp-tRNA(Trp) concentrations in vivo and, in the same cultures, measured rates of protein synthesis in isogenic stringent and relaxed strains. We have also manipulated cellular charged and uncharged [tRNA(Trp)] by two means: (i) the strain used contains a Trp-tRNA synthetase mutation that increases the Km for Trp; thus, varying exogenous Trp varies cellular Trp-tRNA(Trp); and (ii) we have introduced into the mutant strain a plasmid containing the tRNA(Trp) gene behind an inducible promoter; thus, total [tRNA(Trp)] also can be varied depending on length of induction. The use of these conditions, combined with a previously characterized assay system, has allowed us to demonstrate that (i) the rate of incorporation of Trp into protein is proportional to the fraction of tRNA(Trp) that is charged; for any given total [tRNA(Trp)], this rate is also proportional to the [Trp-tRNA(Trp)]; (ii) uncharged tRNA(Trp) inhibits incorporation of Trp into protein; and (iii) rates of incorporation into protein of at least two other amino acids, Lys and Cys, are also sensitive to [Trp-tRNA(Trp)] and are inhibited by uncharged tRNA(Trp). Our results are consistent with models of translational control that postulate modulating polypeptide chain elongation efficiency by varying concentrations of specific tRNAs.

Effect of variation of charged and uncharged tRNA(Trp) levels on ppGpp synthesis in Escherichia coli

We introduced into a stringent Escherichia coli tryptophan auxotroph a plasmid bearing the tRNA(Trp) gene under the control of an inducible promoter. This allows us to manipulate the total concentration of tRNA(Trp) in the cell according to whether and when inducer is added to the culture. We also manipulated the concentration of Trp-tRNA(Trp) in vivo since the strain used bears a mutation in the Trp-tRNA synthetase affecting the Km for tryptophan, such that varying the exogenous concentration of tryptophan led to variation in the level of Trp-tRNA(Trp) in the cell. With this system, we found that the signal eliciting ppGpp synthesis during a stringent response triggered by tryptophan limitation did not depend on the absolute concentration of either charged or uncharged tRNA(Trp) but rather depended on a decline in the ratio of charged/uncharged tRNA(Trp). In addition, we found that the amplitude of the response, once triggered by tryptophan limitation, was determined by the total concentration of tRNA(Trp) present in the cell (which is mostly uncharged at that point in time). However, excess uncharged tRNA(Trp) did not amplify ppGpp synthesis triggered by limitation of a different amino acid. These data provide in vivo support for the in vitro-derived model of ppGpp synthesis on ribosomes.