Lung Tumor Lines Research Articles

Polyclonal antibody-induced downregulation of HER1/EGFR and HER2 surpasses the effect of combinations of specific registered antibodies

Antitumor therapies targeting HER1/EGFR and HER2, such as monoclonal antibodies (MAbs) and tyrosine-kinase inhibitors (TKIs), have demonstrated a significant clinical benefit, but the emergence of resistance limits long-term efficacy. While secondary HER1 mutations confer tolerance to TKI, compensatory upregulation of HER2 drives resistance to anti-HER1 MAbs, which identifies MAb combinations targeting both receptors as an attractive therapeutic strategy. Nevertheless, toxicity hampers the clinical validation of this approach. Alternatively, cancer vaccines may induce antibodies directed against several antigens with less concern about induced toxicity. Polyclonal antibodies (PAbs) targeting HER1 and HER2 were induced in mice or rabbits through immunization. Recognition of different epitopes on targets by PAbs was validated by phage-display technology. Receptor downregulation was evaluated by flow cytometry, immunofluorescence, and Western blot. MTT assays assessed cytotoxicity, while the antitumor effect of PAbs was assayed in nude mice. PAbs promoted degradation of HER1 and HER2 regarding clinical MAbs or their combinations. As a result, inhibition of cytotoxicity on tumor cell lines was improved, even in the presence of oncogenic mutations in HER1, as well as in cetuximab-insensitive cells. Accordingly, the antitumor effect of vaccination-induced PAbs was observed in lung tumor lines representative of sensitivity or resistance to HER1 targeting therapies. Immunization against HER1 and HER2 receptors offers an alternative to passive administration of combinations of MAbs, since vaccination-induced PAbs promote the downregulation of both receptors and they have a higher impact on the survival of tumor cells.

Abstract 5848: Inhibition of the CRM1 nuclear export protein can treat mutant KRAS tumors through stabilizing the DLC1 tumor suppressor protein

Abstract Mutant KRAS is found in >30% of lung adenocarcinomas, and tumors with mutant KRAS usually have poor outcomes with current therapies. The rationale for the new treatment approach described here for tumors with mutant KRAS arises from the critical antitumor role that we have uncovered for reactivating the DLC1 tumor suppressor protein, which is frequently downregulated in a wide range of human cancers. Although several mechanisms account for DLC1 downregulation, here we have focused on a subset of mutant KRAS lung tumor lines that express wild type DLC1 mRNA but lack detectable DLC1 protein. We have recently reported that cytoplasmic EZH2 protein directly methylates Lysine-678 of DLC1 protein leading to its ubiquitination by CUL-4A and consequently, proteasomal degradation. In this study, we have found a specific inhibitor of CRM1 protein (Chromosomal Region Maintenance 1, also known as Exportin 1 [XPO1]) substantially reduces cytoplasmic EZH2 level in several mutant KRAS lung cancer cell lines demonstrating that cytoplasmic EZH2 depends on its nuclear export by CRM1. CRM1, which is the major mammalian nuclear export regulator, is frequently overexpressed and/or mutated in human cancer, including lung adenocarcinomas, and these phenotypes are associated with poor prognosis. Endogenous CRM1 and EZH2 protein colocalized and formed a complex in several lung cancer lines and patient-derived tumor xenografts implying the cancer relevance of this interaction. In addition to blocking the cytoplasmic export of EZH2, pharmacologic inhibition of CRM1 increased the steady-state level of DLC1 protein in several mutant KRAS lung cancer lines and patient-derived xenografts. The tumor suppressor activity of the post-translationally stabilized DLC1 protein was further increased by kinase inhibitors of AKT and SRC, which reverse the direct phosphorylation and attenuation of DLC1 tumor suppressor functions by these kinases. The three-drug combination of inhibitors of CRM1 (Selinexor), AKT (MK-2206), and SRC (Saracatinib), which is well-tolerated in mice, induced potent inhibition of tumor xenograft growth and was associated with induction of markers of apoptosis and senescence. Although each of these inhibitors has multiple targets, CRISPR/Cas9 knockout of DLC1 abolished most of the tumor growth inhibitory activity of the three-drug combination, strongly suggesting that DLC1 is the predominant target for the antitumor activity of the drug combination. Interestingly, KRAS siRNA knockdown phenocopied CRM1 inhibition, as it reduced cytoplasmic EZH2, DLC1 methylation, and DLC1 degradation. Our findings suggest CRM1 inhibitors, when given in conjunction with AKT and/or SRC kinase inhibitors, may have clinical efficacy against lung tumors with mutant KRAS. Citation Format: Brajendra K. Tripathi, Nicole Hirsh, Xiaolan Qian, Dunrui Wang, Marian E. Durkin, Fernando J. de Miguel, Katerina Politi, James H. Doroshow, Douglas R. Lowy. Inhibition of the CRM1 nuclear export protein can treat mutant KRAS tumors through stabilizing the DLC1 tumor suppressor protein [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 5848.

Highlights from Recent Cancer Literature

Highlights from Recent Cancer Literature

Abstract LB-058: GB-3103, an epigenetic immunomodulator, shows potent antitumor activity against tumors harboring dual loss of SMARCA4/SMARCA2 ATPases

Abstract Dual loss of SMARCA4/SMARCA2 ATPases of the SWItch/Sucrose Non-Fermentable (SWI/SNF) complex has been reported in small cell carcinoma of the ovary, hypercalcemic type (SCCOHT) and other tumors. Loss of SMARCA4 is the result of inactivating mutations, and the loss of SMARCA2 results from the absence of mRNA expression. Restoration of either SMARCA4 or SMARCA2 can inhibit the growth of these cancers. We have evaluated the activity of a novel, structurally rigid, and potent, Class I/IIb HDAC inhibitor, GB-3103, against human SCCOHT and other cells lines deficient in SWI/SNF complex. GB-3103 shows potent anti-proliferative activities with low nM IC50 values against human SCCOHT lines BIN67 (51nM), COV434 (35nM) and SCCOHT-1 (293nM), and SWI/SNF-deficient rhabdoid and lung tumor lines A204 (95nM), A427 (174nM), G401 (138 nM), G402 (71nM), H522 (102nM). Treatment of human BIN67 SCCOHT cell line for 72h with GB-3103 revealed potent concentration- and time-dependent induction of SMARCA2 expression at both mRNA and protein levels. Treatment of mice bearing G401 human malignant rhabdoid tumor xenografts with GB-3103 at 5 mg/kg, QD resulted in 70% tumor growth inhibition (TGI) compared to vehicle control (P<0.05). Treatment of mice bearing BIN67 human tumor xenografts with GB-3103 at 5 mg/kg and 10 mg/kg, QD resulted in mean tumor regression of 26% and 33%, respectively, at two weeks post-treatment initiation. RNA-Seq analyses of BIN67 cells treated with GB-3103 revealed that GB-3103 affects DNA replication and mRNA stability as well as inducing the expression of MHC Class II proteins. Given the importance of MHC Class II expression and response to checkpoint inhibitor therapies, we tested the activity of GB-3103 alone and in combination with anti-mPD-1 and anti-mPD-L1 antibodies in a syngeneic CT-26 mouse colon cancer model. GB-3103 induced a 93% TGI as a single agent and caused regression of established CT-26 tumors when combined with either anti-mPD-1 or anti-mPD-L1 demonstrating the potent immunomodulatory activity of GB-3103 in addition to direct anticancer activities. GB-3103 is a novel epigenetic immunomodulator with potent anticancer activity against SWI/SNF-deficient cancers. Clinical development of GB-3103 in these genetically defined rare cancers for which no treatments currently exist provides unique clinical and regulatory opportunity for breakthrough therapy designation where approval could be based on smaller single arm clinical studies. Citation Format: Tong Wang, Paul Gonzales, Kari Kotlarczyk, Myung-Ja Lee, Erin Bossert, Courtney Devore, Haiyong Han, Jessica Lang, William Hendricks, Jeffrey Trent, Stephen Gately. GB-3103, an epigenetic immunomodulator, shows potent antitumor activity against tumors harboring dual loss of SMARCA4/SMARCA2 ATPases [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 LB-058.

Humanization of JAA-F11, a Highly Specific Anti-Thomsen-Friedenreich Pancarcinoma Antibody and InVitro Efficacy Analysis

JAA-F11 is a highly specific mouse monoclonal to the Thomsen-Friedenreich Antigen (TF-Ag) which is an alpha-O-linked disaccharide antigen on the surface of ~80% of human carcinomas, including breast, lung, colon, bladder, ovarian, and prostate cancers, and is cryptic on normal cells. JAA-F11 has potential, when humanized, for cancer immunotherapy for multiple cancer types. Humanization of JAA-F11, was performed utilizing complementarity determining regions grafting on a homology framework. The objective herein is to test the specificity, affinity and biology efficacy of the humanized JAA-F11 (hJAA-F11). Using a 609 target glycan array, 2 hJAA-F11 constructs were shown to have excellent chemical specificity, binding only to TF-Ag alpha-linked structures and not to TF-Ag beta-linked structures. The relative affinity of these hJAA-F11 constructs for TF-Ag was improved over the mouse antibody, while T20 scoring predicted low clinical immunogenicity. The hJAA-F11 constructs produced antibody-dependent cellular cytotoxicity in breast and lung tumor lines shown to express TF-Ag by flow cytometry. Internalization of hJAA-F11 into cancer cells was also shown using a surface binding ELISA and confirmed by immunofluorescence microscopy. Both the naked hJAA-F11 and a maytansine-conjugated antibody (hJAA-F11-DM1) suppressed in vivo tumor progression in a human breast cancer xenograft model in SCID mice. Together, our results support the conclusion that the humanized antibody to the TF-Ag has potential as an adjunct therapy, either directly or as part of an antibody drug conjugate, to treat breast cancer, including triple negative breast cancer which currently has no targeted therapy, as well as lung cancer.

Abstract 4967: RAF kinase inhibition synergizes with MEK inhibitors in KRAS mutant tumors

Abstract While activating mutations in the KRAS oncogene frequently drive tumorigenesis in human cancers (40% CRC, 20% NSCLC) through constitutive activation of the MAPK pathway, there are currently no targeted treatments available for KRAS mutant cancers. Inhibitors of the individual nodes of the MAPK pathway have been developed, but these molecules have been largely ineffective against KRAS mutant tumors in the clinic. Multiple studies have shown rational combinations of MAPK inhibitors may have anti-tumor activity in KRAS mutant models. In order to understand the versatility of combining RAF inhibitors in this context, we conducted a library screen consisting of 430 small molecule tool compounds in combination with RAF inhibitor AZ-628. Here we show: RAF inhibitors combine especially well with other MAPK pathway inhibitors in KRAS mutant tumor cells. In particular, Type II RAF inhibitors are synergistic with the MEK inhibitor Cobimetinib in vitro and exhibit tumor regressing efficacy in xenograft mouse model studies in vivo. Mechanistically, we have found the MEK inhibitor disables ERK induced negative feedback on the MAPK pathway resulting in activation of CRAF in a KRAS dependent manner. The combination of RAF with MEK inhibition blunts KRAS-dependent activation of CRAF kinase activity and robustly inhibits MAPK signaling, thereby driving efficacy in KRAS mutant tumors. Broad cell line profiling with the combination of RAF and MEK inhibitors demonstrates that a majority of KRAS mutant lung and colorectal tumor lines exhibit synergy with the combination. Therefore, combining a Type II pan-RAF inhibitor with a MEK inhibitor has the potential to improve the therapeutic outcome in KRAS mutant cancers. Citation Format: Ivana Yen, Christiaan Klijn, Frances Shanahan, Mark Merchant, Christine Orr, Thomas Hunsaker, Matthew Durk, Hank La, Xiaolin Zhang, Scott Martin, Eva Lin, John Chan, Yihong Yu, Amy Gustafson, Joachim Rudolph, Shiva Malek. RAF kinase inhibition synergizes with MEK inhibitors in KRAS mutant tumors [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 4967. doi:10.1158/1538-7445.AM2017-4967

3-Oxo-γ-costic acid fungal-transformation generates eudesmane sesquiterpenes with in vitro tumor-inhibitory activity

While select eudesmane sesquiterpenes exhibit anti-neoplastic activity, tumor-inhibition for costic-acids has not been established. Here biological activity of 3-oxo-γ-costic acid (1), previously isolated from Chiliadenus montanus, as well as new sesquiterpenes (2–5) and the known derivative, 3-oxoeudesma-1,4,11(13)-trien-7-1061αH-l2-oic acid (6), all produced from 1 by the fungus Athelia rolfsii, are reported. Structures were elucidated using MS and NMR spectroscopy with activity-screening utilizing human colon- and lung-tumor lines, Caco-2 and A549 respectively. Compound 1 exhibited anti-proliferative activity against Caco-2 (IC50 39µM) and 2 was active against A549 (IC50 74µM) suggesting therapeutic potential for the original substrate and a bio-transformed product.

Kinome sequencing reveals RET G691S polymorphism in human neuroendocrine lung cancer cell lines.

Neuroendocrine (NE) lung tumors comprise 20-25% of all invasive lung malignancies. Currently, no effective treatments are available to cure these tumors, and it is necessary to identify a molecular alteration(s) that characterizes NE lung tumor cells. We aimed to identify a kinase mutation(s) associated with NE lung tumor by screening 517 kinase-encoding genes in human lung cancer cell lines. Our next-generation sequencing analysis of six NE lung tumor cell lines (four small cell lung cancer lines and two non-small cell lung cancer lines) and three non-NE lung tumor lines revealed various kinase mutations, including a nonsynonymous mutation in the proto-oncogene RET (c.2071G>A; p.G691S). Further evaluation of the RET polymorphism in total 15 lung cancer cell lines by capillary sequencing suggested that the frequency of the minor allele (A-allele) in NE lung tumor lines was significantly higher than its frequency in a reference population (p = 0.0001). However, no significant difference between non-NE lung tumor lines and a reference group was detected (p = 1.0). Nevertheless, neither RET expression levels were correlated with the levels of neuron-specific enolase (NSE), a key NE marker, nor vandetanib and cabozantinib, small molecule compounds that inhibit RET, affected NSE levels in lung cancer cells. Our data suggest a potential association of G691S RET polymorphism with NE lung tumor, proposing the necessity of more thorough evaluation of this possibility. The dataset of kinase mutation profiles in this report may help choosing cell line models for study of lung cancer.

Membrane versus Soluble Isoforms of TNF-α Exert Opposing Effects on Tumor Growth and Survival of Tumor-Associated Myeloid Cells

TNF-α, produced by most malignant cells, orchestrates the interplay between malignant cells and myeloid cells, which have been linked to tumor growth and metastasis. Although TNF-α can exist as one of two isoforms, a 26-kDa membrane tethered form (mTNF-α) or a soluble 17-kDa cytokine (sTNF-α), the vast majority of published studies have only investigated the biologic effects of the soluble form. We show for the first time that membrane and soluble isoforms have diametrically opposing effects on both tumor growth and myeloid content. Mouse lung and melanoma tumor lines expressing mTNF-α generated small tumors devoid of monocytes versus respective control lines or lines expressing sTNF-α. The lack of myeloid cells was due to a direct effect of mTNF-α on myeloid survival via induction of cell necrosis by increasing reactive oxygen species. Human non-small cell lung carcinoma expressed varying levels of both soluble and membrane TNF-α, and gene expression patterns favoring mTNF-α were predictive of improved lung cancer survival. These data suggest that there are significant differences in the role of different TNF-α isoforms in tumor progression and the bioavailability of each isoform may distinctly regulate tumor progression. This insight is critical for effective intervention in cancer therapy with the available TNF-α inhibitors, which can block both TNF-α isoforms.

Abstract 5726: Human epidermal growth factor 3 (HER3) blockade with U3-1287/AMG888 modulates radiosensitivity in the lung and head and neck carcinomas

Abstract The epidermal growth factor receptor (EGFR) family consists of four members including HER1 (EGFR), HER2 (ErbB2), HER3 (ErbB3) and HER4 (ErbB4). Collectively this family of receptor tyrosine kinases (RTKs) play critical roles in the etiology of several human cancers as well as a role in resistance to radiation therapy. In 2006, a study in head and neck squamous cell carcinoma (HNSCC) indicated that using the anti-EGFR antibody cetuximab in combination with radiation resulted in a 10% advantage of 3-year overall survival rate when compared to radiotherapy alone. This study highlighted the therapeutic utility of RTK blockade in combination with radiation. Studies investigating the role of HER3 in radiation response are limited. In the present study, we investigated whether or not HER3 blockade could enhance radiation therapy using the HER3 antibody U3-1287/AMG888. We screened a battery of cell lines from lung, HNSCC and colorectal tumor lines for HER3 expression. The results indicated that all 15 cell lines tested showed expression of HER3. In addition, U3-1287/AMG888 was able to block basal HER3 activity and radiation induced HER3 activation. Further, proliferation assays, using U3-1287/AMG888, indicated that HER3 blockade could block proliferation in SCC6, SCC1483, H226 cell lines, highlighting the importance of HER3 in these tumor cells. Clonogenic assays showed that U3-1287/AMG888 could sensitize these lines to radiation. Furthermore, γ-H2AX analyses, detected by immunofluorescence, lead to a statistically significant increase in apoptotic cells. Cell cycle analysis, 24 and 48 hours after U3-1287/AMG888 and radiation treatments resulted in a significant G1 and G2 cell cycle arrest. Annexin-V binding assays showed a significant increase in apoptosis in the U3-1287/AMG888 plus radiation group as compared to either agent alone. To determine if HER3 blockade using U3-1287/AMG888 could enhance radiation therapy in vivo we performed tumor growth delay experiments using SCC6, SCC1483 and H226 xenografts in nude mice. Mice were inoculated and treated with 1) IgG, 2) U3-1287/AMG888, 3) radiation or 4) the combination. The results of these experiments indicated that the combination of U3-1287/AMG888 and radiation had a strong impact on tumor growth in studies using single dose or fractionated dosing. Tumor analysis indicated that radiation treatment activated HER3 in vivo and U3-1287/AMG888 could abrogate this activation. Collectively our findings in vitro and in vivo suggest that U3-1287/AMG888 in combination with radiation has an impact on cell and tumor growth by impacting cell cycle progression, increasing apoptosis and increasing DNA damage. These findings suggest that HER3 may play a critical role in response to radiation therapy and blocking its activity may be of strong therapeutic benefit in human tumors. 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 5726. doi:1538-7445.AM2012-5726

Abstract C211: Therapeutic utility of GSK-3 inhibitors for the treatment of cancer

Abstract Glycogen synthase kinase-3 (GSK-3) is a constitutively active protein kinase that plays a role in diverse signaling pathways. Initially described as a regulator of glycogen synthesis and metabolism, GSK-3 is now known to play a central role in a variety of cellular functions ranging from maintenance of stem cell function to regulation of cell cycle and apoptosis. In mammals, there are two highly homologous isoforms of GSK-3 (GSK-3α and GSK-3β) which share substrate specificity and functional properties. GSK3β is one of the key components of the β-catenin destruction complex and phosphorylation of β-catenin by GSK-3 targets the substrate protein for ubiquitylation and proteosomal destruction - conversely, inhibition of GSK-3β activity results in loss of phosphorylation sites and stabilization of β-catenin in the cellular cytoplasm and nucleus. GSK-3 expression and/or activity have been reported to be elevated in multiple tumor types, including pancreatic, gastric and colorectal carcinomas. Equally important, inhibition of GSK-3 expression in colorectal tumor cell lines via specific siRNAs induced apoptosis and attenuated the proliferation of tumor cells. Together, these findings suggest that GSK-3 inhibitors may represent a new class of therapeutic agents against colorectal cancer. LY-GSK-3i is a novel, potent and selective ATP competitive inhibitor of both isoforms of GSK-3. In vitro, LY potently inhibits the enzymatic activity of GSK-3α and GSK-3β with IC50s of 1.5 nM and 0.9 nM, respectively. Pharmacologic activity of other GSK-3 inhibitors in the literature against cancer is not clear. LY-GSK-3i did not evidence useful antitumor activity in its own right against colorectal, ovarian or non-small cell lung (NSCL) tumor lines. However, when combined with different chemotherapeutic agents, LY was found to potentiate their pro-apoptotic activity. LY-GSK-3i was shown to significantly potentiate caspase-3 activation when combined cisplatin in HCT-116 and Colo-205 colorectal carcinoma lines. Enhancement of caspase-3 activity was also observed when LY-GSK-3i was combined with 5-fluorouracyl (5-FU) in HCT-116 cells. In order to explore the potential of LY-GSK-3i in other tumor types, we assessed the pro-apoptotic activity of the LY/cisplatin combination against ovarian (A2780) and lung (A549 and NCI-H460) cell lines. In all cases, LY-GSK-3i was shown to significantly elevate caspase-3 activity when compared to cisplatin alone. In vivo, administration of a single dose of LY-GSK-3i to xenograft-bearing mice lead to a time-and dose-dependent accumulation of the substrate protein -catenin in tumor tissues. In vivo xenograft growth studies revealed that administration of 5 mg/kg LY-GSK-3i in combination with cisplatin, given every 7 or 14 days, was sufficient to significantly improve the efficacy as compared to cisplatin alone given at the same intervals. Together, our findings provide evidence for the potential therapeutic utility of GSK-3 inhibitors for the treatment of cancer. Citation Information: Mol Cancer Ther 2009;8(12 Suppl):C211.

Induction of E-Cadherin in Lung Cancer and Interaction with Growth Suppression by Histone Deacetylase Inhibition

Loss of E-cadherin confers a poor prognosis in lung cancer patients and is associated with in vitro resistance to endothelial growth factor receptor inhibitors. Zinc finger E box-binding homeobox (ZEB)-1, the predominant transcriptional suppressor of E-cadherin in lung tumor lines, recruits histone deacetylases (HDACs) as co-repressors. NSCLC cell lines were treated with HDAC inhibitors and analyzed for E-cadherin induction, growth inhibition and apoptosis. National Cancer Institute-H157 cells expressing ectopic E-cadherin were tested for tumorigenicity in murine xenografts. We found that treatment with MS-275, compared to vorinostat (SAHA), valproic acid or trichostatin A, was most effective in E-cadherin up-regulation and persistence in non-small cell lung cancers. As with other tumor types and HDAC inhibitors, MS-275 inhibited growth and induced apoptosis. Importantly, blocking E-cadherin induction by short hairpin RNA resulted in less inhibition by MS-275, implicating the epithelial to mesenchymal phenotype process as a contributing factor. In contrast to H460 and H661, H157 cells were resistant to E-cadherin up-regulation by HDAC inhibitors. However, E-cadherin was restored, in a synergistic manner, by combined knockdown of ZEB-1 and ZEB-2. In addition, H157 cells stably transfected with E-cadherin were markedly attenuated in their tumor forming ability. Lastly, combining MS-275 with the microtubule stabilizing agent, paclitaxel, or 17-(allylamino)-17-demethoxygeldanamycin, a heat shock protein 90 inhibitor, resulted in synergistic growth inhibition. Since MS-275 has no reported activity against HDAC6, which regulates both microtubule and heat shock protein 90 functions, other mechanisms of synergy are anticipated. These results support the role of ZEB proteins and HDAC inhibitors in the pathogenesis and treatment of lung cancer.

Development of Arterial Blood Supply in Experimental Liver Metastases

In this study, we present a mechanism for the development of arterial blood supply in experimental liver metastases. To analyze the arterialization process of experimental liver metastases, we elucidated a few key questions regarding the blood supply of hepatic lobules in mice. The microvasculature of the mouse liver is characterized by numerous arterioportal anastomoses and arterial terminations at the base of the lobules. These terminations supply one hepatic microcirculatory subunit per lobule, which we call an arterial hepatic microcirculatory subunit (aHMS). The process of arterialization can be divided into the following steps: 1) distortion of the aHMS by metastasis; 2) initial fusion of the sinusoids of the aHMS at the tumor parenchyma interface; 3) fusion of the sinusoids located at the base of the aHMSs, which leads to the disruption of the vascular sphincter (burst pipe); 4) incorporation of the dilated artery and the fused sinusoids into the tumor; and 5) further development of the tumor vasculature (arterial tree) by proliferation, remodeling, and continuous incorporation of fused sinusoids at the tumor-parenchyma interface. This process leads to the inevitable arterialization of liver metastases above the 2000- to 2500-mum size, regardless of the origin and growth pattern of the tumor.

Discovery of Inhibitors that Elucidate the Role of UCH-L1 Activity in the H1299 Lung Cancer Cell Line

Neuronal ubiquitin C-terminal hydrolase (UCH-L1) has been linked to Parkinson's disease (PD), the progression of certain nonneuronal tumors, and neuropathic pain. Certain lung tumor-derived cell lines express UCH-L1 but it is not expressed in normal lung tissue, suggesting that this enzyme plays a role in tumor progression, either as a trigger or as a response. Small-molecule inhibitors of UCH-L1 would be helpful in distinguishing between these scenarios. By utilizing high-throughput screening (HTS) to find inhibitors and traditional medicinal chemistry to optimize their affinity and specificity, we have identified a class of isatin O-acyl oximes that selectively inhibit UCH-L1 as compared to its systemic isoform, UCH-L3. Three representatives of this class (30, 50, 51) have IC 50 values of 0.80–0.94 μM for UCH-L1 and 17–25 μM for UCH-L3. The K i of 30 toward UCH-L1 is 0.40 μM and inhibition is reversible, competitive, and active site directed. Two isatin oxime inhibitors increased proliferation of the H1299 lung tumor cell line but had no effect on a lung tumor line that does not express UCH-L1. Inhibition of UCH-L1 expression in the H1299 cell line using RNAi had a similar proproliferative effect, suggesting that the UCH-L1 enzymatic activity is antiproliferative and that UCH-L1 expression may be a response to tumor growth. The molecular mechanism of this response remains to be determined.

NORE1A, a homologue of RASSF1A tumour suppressor gene is inactivated in human cancers.

We recently demonstrated that RASSF1A, a new tumour-suppressor gene located at 3p21.3 is frequently inactivated by promoter region hypermethylation in a variety of human cancers including lung, breast, kidney and neuroblastoma. We have identified another member of the RASSF1 gene family by in silico sequence analysis using BLAST searches. NORE1 located at 1q32.1 exists in three isoforms (NORE1Aalpha, NORE1Abeta and NORE1B). Both NORE1A and NORE1B isoforms have separate CpG islands spanning their first exons. NORE1Aalpha Produces a 418 aa protein containing a Ras-association (RA) domain and a diacylglycerol (DAG) binding domain. NORE1Abeta produces a C-terminal truncation of the RA domain. NORE1B also contains the RA domain but not the DAG domain. NORE1 is the human homologue of the mouse Ras effector Nore1. No inactivating somatic mutations were found in lung tumour lines; however, NORE1A promoter region CpG island was hypermethylated in primary tumours and tumour cell lines. NORE1A promoter was methylated in 10/25 breast, 4/40 SCLC, 3/17 NSCLC, 1/6 colorectal and 3/9 kidney tumour cell lines, while NORE1B promoter was unmethylated in the same tumour cell lines. While 24% (6/25) of primary NSCLC underwent NORE1A methylation, methylation in SCLC was a rare event (0/22); (P = 0.0234). NORE1A expression in tumour cell lines was reactivated after treatment with a demethylating agent. There was no correlation between NORE1A and RASSF1A methylation status in NSCLC. Our results demonstrate that NORE1A is inactivated in a subset of human cancers by CpG island promoter hypermethylation, and in lung cancer this hypermethylation may be histological type specific.

Frequent 3p allele loss and epigenetic inactivation of the RASSF1A tumour suppressor gene from region 3p21.3 in head and neck squamous cell carcinoma

Studies of allelic imbalance and suppression of tumourigenicity have consistently suggested that the short arm of chromosome three (3p) harbours tumour suppressor genes (TSGs) whose inactivation leads to the development of various types of neoplasia including head and neck squamous cell carcinoma (HNSCC). Previously, we defined a critical minimal region of 120kb at 3p21.3 that contains overlapping homozygous deletions in lung and breast tumour lines and isolated eight genes from the minimal region. Mutation analysis in a large panel of lung and breast cancers revealed only rare mutations, but the majority of lung tumour lines showed loss of expression for one of the eight genes ( RASSF1A) due to hypermethylation of a CpG island in the promoter region of RASSF1A. We found RASSF1A to be methylated in the majority of lung tumours, but to a lesser extent in breast and ovarian tumours. In order to define the role of 3p TSGs, in particular RASSF1A in HNSCC, we (a) analysed 43 primary HNSCC for allelic loss in regions proposed to contain 3p TSGs (3p25-26, 3p24, 3p21-22, 3p14 and 3p12), (b) analysed 24 HNSCC for evidence of RASSF1A methylation and (c) undertook mutation analysis of RASSF1A in HNSCC. We found that 81% of HNSCC showed allele loss at one or more 3p markers, 66% demonstrated loss for 3p21.3 markers and 56% showed allelic losses at 3p12 loci. Thus, 3p loss is common in HNSCC and extensive 3p loss occurs even in early stage tumours. RASSF1A promoter region hypermethylation was found in 17% (4/24) of the sporadic HNSCC, but RASSF1A mutations were not identified. Furthermore, we found RASSF1A methylation to be significantly higher in poorly differentiated then in moderate to well differentiated HNSCC ( P=0.0048). Three of the four tumours showing RASSF1A methylation also underwent 3p21.3 allelic loss, hence RASSF1A behaves as a classical TSG (two hits, methylation and loss). One tumour with RASSF1A methylation had retention of markers at 3p providing further evidence of specific inactivation of RASSF1A as a critical step in some HNSCC. Although the frequency of 3p21.3 allele loss was substantially higher than that of RASSF1A methylation this does not necessarily suggest that other genes from 3p21.3 are also implicated in HNSCC, as 3p21.3 LOH was invariably found with LOH at other 3p loci. Thus, the presence of 3p21.3 allele loss without RASSF1A methylation might reflect a propensity for 3p21.3 loss to occur as a secondary consequence of large 3p deletions targeted at other 3p TSG regions. Furthermore, in the presence of homozygous inactivation of other 3p TSGs, RASSF1A haploinsufficiency might be sufficient to promote tumourigenesis in many HNSCC.

RASSF1A promoter region CpG island hypermethylation in phaeochromocytomas and neuroblastoma tumours.

Deletions of chromosome 3p are frequent in many types of neoplasia including neural crest tumours such as neuroblastoma (NB) and phaeochromocytoma. Recently we isolated several candidate tumour suppressor genes (TSGs) from a 120 kb critical interval at 3p21.3 defined by overlapping homozygous deletions in lung and breast tumour lines. Although mutation analysis of candidate TSGs in lung and breast cancers revealed only rare mutations, expression of one of the genes (RASSF1A) was absent in the majority of lung tumour cell lines analysed. Subsequently methylation of a CpG island in the promoter region of RASSF1A was demonstrated in a majority of small cell lung carcinomas and to a lesser extent in non-small cell lung carcinomas. To investigate the role of 3p TSGs in neural crest tumours, we (a) analysed phaeochromocytomas for 3p allele loss (n=41) and RASSF1A methylation (n=23) and (b) investigated 67 neuroblastomas for RASSF1A inactivation. 46% of phaeochromocytomas showed 3p allele loss (38.5% at 3p21.3). RASSF1A promoter region hypermethylation was found in 22% (5/23) of sporadic phaeochromocytomas and in 55% (37/67) of neuroblastomas analysed but RASSF1A mutations were not identified. In two neuroblastoma cell lines, methylation of RASSF1A correlated with loss of RASSF1A expression and RASSF1A expression was restored after treatment with the demethylating agent 5-azacytidine. As frequent methylation of the CASP8 gene has also been reported in neuroblastoma, we investigated whether RASSF1A and CASP8 methylation were independent or related events. CASP8 methylation was detected in 56% of neuroblastomas with RASSF1A methylation and 17% without RASSF1A methylation (P=0.0031). These results indicate that (a) RASSF1A inactivation by hypermethylation is a frequent event in neural crest tumorigenesis, particularly neuroblastoma, and that RASSF1A is a candidate 3p21.3 neuroblastoma TSG and (b) a subset of neuroblastomas may be characterized by a CpG island methylator phenotype.

Gene Expression Profiling of Cultured Human Bronchial Epithelial and Lung Carcinoma Cells

Lung cancer is a complex collection of diseases that is thought to begin with single mutated progenitor cells and culminates in any of several clinically described pathologies. Our knowledge of the molecular events that lead to different lung cancer types--small cell carcinoma, squamous cell carcinoma, adenocarcinoma, and large cell carcinoma--is incomplete. Nonetheless, it is evident that genetic changes that impact multiple molecular networks are involved in the generation of each specific phenotype. Due to the obvious complexity of these processes, the simultaneous quantitative monitoring of changes in the expression of genes that define these networks can provide mechanistic information to increase our understanding of the molecular basis for human pulmonary carcinogenesis. To this end, we have employed a commercially available human cDNA array (Atlas Human Array, Clontech Laboratories) to systematically screen for alterations in the expression of 600 genes in normal human bronchial epithelial (NHBE) cells as well as in several lung carcinoma lines. Studies on the reproducibility and variability of array results indicate that a 2-fold or greater difference in the expression of a particular gene could be considered a real difference in transcript abundance. Accuracy of gene expression as measured in the array was verified by comparing mRNA levels of the proto-oncogene c-myc in the array with results obtained by traditional Northern blot analysis and by quantitative RT-PCR. Gene expression profiles were compared within and among cell types. The differential expression of 17 genes, including downregulation of MRP8 and MRP14 and upregulation of CYP1B1, was observed in all four carcinoma lines compared to NHBE cells. The direction of all 17 gene expression differences, either upregulation or downregulation relative to NHBE cells, was the same for all four carcinoma lines, underscoring their common molecular features. Each lung tumor line also exhibited a number of unique differences compared to both normal cells and the other tumor cell lines. These differences may be due to differences in the cellular origin and/or pathology of the cell lines studied.

Methylation associated inactivation of RASSF1A from region 3p21.3 in lung, breast and ovarian tumours.

Previously we analysed overlapping homozygous deletions in lung and breast tumours/tumour lines and defined a small region of 120 kb (part of LCTSGR1) at 3p21.3 that contained putative lung and breast cancer tumour suppressor gene(s) (TSG). Eight genes including RASSF1 were isolated from the minimal region. However, extensive mutation analysis in lung tumours and tumour lines revealed only rare inactivating mutations. Recently, de novo methylation at a CpG island associated with isoform A of RASSF1 (RASSF1A) was reported in lung tumours and tumour lines. To investigate RASSF1A as a candidate TSG for various cancers, we investigated: (a) RASSF1A methylation status in a large series of primary tumour and tumour lines; (b) chromosome 3p allele loss in lung tumours and (c) RASSF1 mutation analysis in breast tumours. RASSF1A promoter region CpG island methylation was detected in 72% of SCLC, 34% of NSCLC, 9% of breast, 10% of ovarian and 0% of primary cervical tumours and in 72% SCLC, 36% NSCLC, 80% of breast and 40% of ovarian tumour lines. In view of the lower frequency of RASSF1 methylation in primary breast cancers we proceeded to RASSF1 mutation analysis in 40 breast cancers. No mutations were detected, but six single nucleotide polymorphisms were identified. Twenty of 26 SCLC tumours with 3p21.3 allelic loss had RASSF1A methylation, while only six out of 22 NSCLC with 3p21.3 allele loss had RASSF1A methylation (P=0.0012), one out of five ovarian and none out of six cervical tumours with 3p21.3 loss had RASSF1A methylation. These results suggest that (a) RASSF1A inactivation by two hits (methylation and loss) is a critical step in SCLC tumourigenesis and (b) RASSF1A inactivation is of lesser importance in NSCLC, breast, ovarian and cervical cancers in which other genes within LCTSGR1 are likely to be implicated.

Expression of apoptosis-regulatory genes in lung tumour cell lines: relationship to p53 expression and relevance to acquired drug resistance.

As a first step towards elucidating the potential role(s) of bcl-2 and bcl-2-related genes in lung tumorigenesis and therapeutic responsiveness, the expression of these genes has been examined in a panel of lung cancer cell lines derived from untreated and treated patients, and in cell lines selected in vitro for multidrug resistance. Bcl-2 was hyperexpressed in 15 of 16 small-cell lung cancer (SCLC) cell lines and two of five non-small-cell lung cancer (NSCLC) lines compared with normal lung and brain, and hyperexpression was not chemotherapy related. Bcl-x was hyperexpressed in the majority of SCLC and NSCLC cell lines as compared with normal tissues, and all lung tumour lines preferentially expressed bcl-x1-mRNA, the splice variant form that inhibits apoptosis. Bax gene transcripts were hyperexpressed in most SCLC and NSCLC cell lines examined compared with normal adult tissues. Mutant p53 gene expression was detected in the majority of the cell lines and no relationship between p53 gene expression and the expression of either bcl-2, bcl-x or bax was observed. No changes in bcl-2, bcl-x and bax gene expression were observed in multidrug-resistant cell lines compared with their drug-sensitive counterparts.