Abstract 3623: Neoadjuvant chemotherapy is associated with increased expression of DNA repair proteins and epithelial to mesenchymal transition (EMT) in patients with non-small cell lung cancer (NSCLC)

Background: Proteomic profiling has elucidated several dysregulated pathways in NSCLC. We sought to identify patterns of protein expression that are enriched following neoadjuvant chemotherapy in patients with resected lung cancers.

Methods: Tissue samples were selected from the PROSPECT trial at MD Anderson Cancer Center, the goal of which was to correlate molecular profiles with treatment response. Samples from 189 patients were analyzed, which included 26% squamous tumors; 27% with neoadjuvant chemotherapy (n = 49); and predominantly localized disease (distribution: I = 91, II = 35, III = 58, IV = 5). Reverse phase protein array (RPPA) analysis was utilized to quantify 127 total or phosphorylated proteins. Interactions between protein expression and the receipt of neoadjuvant chemotherapy were assessed by analysis of variance (ANOVA). Cox regression was performed to determine the relationship between protein expression and recurrence-free survival (RFS).

Results: Twenty one of the 127 proteins (16%) were expressed at significantly different levels in patients receiving neoadjuvant chemotherapy. Specifically, patients receiving neoadjuvant chemotherapy had higher expression of multiple DNA repair proteins, including MSH2 (p<0.001), 53BP1 (p = 0.01), and p-CHK1 (p = 0.02), as was Rb (p = 0.01), which regulates the expression of several proteins involved in DNA repair. Thymidylate synthase (TS), a target of the chemotherapeutic agent pemetrexed, also showed increased expression (p = 0.02). In addition, there was lower expression of phosphorylated proteins in the PI3K pathway, including p-70S6K (p = 0.008), p-mTOR (p = 0.02), and p-PDK (p = 0.02). Finally, we observed an expression of proteins indicative of an epithelial to mesenchymal transition (EMT), with lower expression of E-cadherin (p = 0.007) and Met (p = 0.03). Notably, there was also lower expression of COL6A, an excreted extracellular protein involved in cellular adhesion (p<0.001), and a trend towards significance in increased expression of stathmin (p = 0.06), a microtubule destabilizer that has previously been implicated in EMT. Finally, we found that higher expression of multiple proteins involved in DNA repair were associated with a reduction in RFS after induction chemotherapy, including p-Rb (p = 0.015), CHK1 (p = 0.027), and p-CHK1 (p = 0.049).

Conclusions: The receipt of neoadjuvant chemotherapy was associated with higher expression of DNA repair proteins, suppression of the PI3K pathway, and an EMT shift. Increased expression of DNA repair proteins was also associated with reduced RFS. These findings suggest that higher expression of DNA repair proteins may contribute to treatment resistance, and support the combination of standard chemotherapy with targeted agents such as Chk inhibitors or immunotherapy (to address EMT-mediated immune escape).

Citation Format: Daniel R. Gomez, Lixia Diao, Jing Wang, Ignacio I. Wistuba, Cesar Moran, Neda Kalhor, Milind B. Suraokar, Stephen G. Swisher, Carmen Behrens, Youhong Fan, John V. Heymach, Lauren A. Byers. Neoadjuvant chemotherapy is associated with increased expression of DNA repair proteins and epithelial to mesenchymal transition (EMT) in patients with non-small cell lung cancer (NSCLC). [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 3623. doi:10.1158/1538-7445.AM2015-3623

Abstract 613: Copy number variations distinguish lung adenocarcinomas from squamous cell carcinomas

Purpose

To develop a molecular based classification of non-small cell lung carcinomas based on genome wide copy number variations (CNVs).

Background

For a number of clinical and biologic reasons, the accurate classification of non small cell lung carcinoma (NSCLC) into adenocarcinoma (ADC) and squamous cell carcinoma (SCC) is essential. DNA based tests, which are not currently used, are more robust when applied to formalin fixed paraffin embedded tissues.

Materials and Methods

TCGA Dataset: The Cancer Genome Atlas project (TCGA) level 3 CNVs data (Affymetrix Genome-Wide Human SNP Array 6.0) of resected ADC (n = 241) and SCC (n = 210) patients were utilized as a Training set along with 1091 non malignant lung samples.

SPORE Patient Dataset: The UT Lung SPORE cohort consists of 248 resected lung cancers (168 ADC and 74 SCC samples) run with the Agilent 244K Human Genome CGH Microarray.

Molecular signature identification based on the morphologic subclassification of NSCLC: We used statistical algorithms to identify potential CNV biomarkers and combined them with known amplified oncogenes to identify 28 CNV signature genes that were highly correlated with histological classification.

Identification of CNV classifier genes. The CNV signature genes were identified through the following four sequential steps: 1) Paired t-test. 2) Elastic Net. 3) Partial lease squares algorithm. 4) Naive Bayes classifier.

Results:

The 28 gene CNV signature accurately separated squamous cell carcinomas from adenocarcinomas in the Training and Validation sets as well as distinguished tumors from non-malignant tissues (Table 1).

Table 1. The classification results between ADC and SCC

DataSensitivitySpecificityAccuracyADC vs SCCTraining set (TCGA)0.940.870.91Validation set (SPORE)0.870.840.86Tumor vs Non-malignantADC0.910.960.94SCC0.970.980.98

Conclusions: A 28 gene CNV signature distinguished lung adenocarcinomas from squamous cell carcinomas with great accuracy (86-91%) and the lung tumor samples can be distinguished from the non-malignant lung samples with an accuracy of 94-98%.

Citation Format: Kai Song, Guangqiang Zheng, Luc Girard, Ignacio I. Wistuba, Jack A. Roth, Carmen Behrens, Milind B. Suraokar, John D. Minna, Adi F. Gazdar. Copy number variations distinguish lung adenocarcinomas from squamous cell carcinomas. [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 613. doi:10.1158/1538-7445.AM2015-613

Expression profiling stratifies mesothelioma tumors and signifies deregulation of spindle checkpoint pathway and microtubule network with therapeutic implications

BACKGROUND

Malignant pleural mesothelioma (MPM) is a lethal neoplasm exhibiting resistance to most treatment regimens and requires effective therapeutic options. Though an effective strategy in many cancer, targeted therapy is relatively unexplored in MPM because the therapeutically important oncogenic pathways and networks in MPM are largely unknown.

MATERIALS AND METHODS

We carried out gene expression microarray profiling of 53 surgically resected MPMs tumors along with paired normal tissue. We also carried out whole transcriptomic sequence (RNA-seq) analysis on eight tumor specimens. Taqman-based quantitative Reverse-transcription polymerase chain reaction (qRT-PCR), western analysis and immunohistochemistry (IHC) analysis of mitotic arrest deficient-like 1 (MAD2L1) was carried out on tissue specimens. Cell viability assays of MPM cell lines were carried out to assess sensitivity to specific small molecule inhibitors.

RESULTS

Bioinformatics analysis of the microarray data followed by pathway analysis revealed that the mitotic spindle assembly checkpoint (MSAC) pathway was most significantly altered in MPM tumors with upregulation of 18 component genes, including MAD2L1 gene. We validated the microarray data for MAD2L1 expression using quantitative qRT-PCR and western blot analysis on tissue lysates. Additionally, we analyzed expression of the MAD2L1 protein by IHC using an independent tissue microarray set of 80 MPM tissue samples. Robust clustering of gene expression data revealed three novel subgroups of tumors, with unique expression profiles, and showed differential expression of MSAC pathway genes. Network analysis of the microarray data showed the cytoskeleton/spindle microtubules network was the second-most significantly affected network. We also demonstrate that a nontaxane small molecule inhibitor, epothilone B, targeting the microtubules have great efficacy in decreasing viability of 14 MPM cell lines.

CONCLUSIONS

Overall, our findings show that MPM tumors have significant deregulation of the MSAC pathway and the microtubule network, it can be classified into three novel molecular subgroups of potential therapeutic importance and epothilone B is a promising therapeutic agent for MPM.

DeMix: deconvolution for mixed cancer transcriptomes using raw measured data

MOTIVATION

Tissue samples of tumor cells mixed with stromal cells cause underdetection of gene expression signatures associated with cancer prognosis or response to treatment. In silico dissection of mixed cell samples is essential for analyzing expression data generated in cancer studies. Currently, a systematic approach is lacking to address three challenges in computational deconvolution: (i) violation of linear addition of expression levels from multiple tissues when log-transformed microarray data are used; (ii) estimation of both tumor proportion and tumor-specific expression, when neither is known a priori; and (iii) estimation of expression profiles for individual patients.

RESULTS

We have developed a statistical method for deconvolving mixed cancer transcriptomes, DeMix, which addresses the aforementioned issues in array-based expression data. We demonstrate the performance of our model in synthetic and real, publicly available, datasets. DeMix can be applied to ongoing biomarker-based clinical studies and to the vast expression datasets previously generated from mixed tumor and stromal cell samples.

AVAILABILITY

All codes are written in C and integrated into an R function, which is available at http://odin.mdacc.tmc.edu/∼wwang7/DeMix.html.

CONTACT

wwang7@mdanderson.org

SUPPLEMENTARY INFORMATION

Supplementary data are available at Bioinformatics online.

Abstract 5589: Molecular signatures of in vitro drug response in lung cancer

We are developing in vitro drug response signatures based on profiling of mRNA (Illumina WG6-V3 arrays), DNA mutation (COSMIC and deep sequencing), DNA copy number (Illumina Human1M-Duov3 SNP array) and DNA methylation (Illumina HumanMethylation450) from lung cancer cell lines to predict which drugs a patient's tumor is most likely to respond to. We have generated drug response phenotypes (MTS colorimetric assays) for ∼25 standard, targeted, and new chemotherapy agents and combinations for ∼ 100 non-small cell lung cancer (NSCLC) lines. All assays were done in triplicates or more and were very reproducible over time (r > 0.8). More than 10,000 MTS assays were generated and we designed a high-throughput database software named DIVISA (Database of In VItro Sensitivity Assays) for the purpose of storing and analyzing these assays. Some drugs showed a wide range of sensitivities (> 10,000-fold in IC50 values) and IC50 clustering indicates that drug response phenotypes can be grouped according to drug types. As part of a joint NCI SPORE, NCI SPECS, and DOD PROSPECT effort we have collected 275 clinically annotated frozen tumors with drug response information including 94 that represent lung cancer resection followed by adjuvant treatment. These specimens have also been profiled on Illumina expression arrays to formally test the clinical relevance of the tumor cell line signatures, and to verify that the signatures predict for response only in the presence of treatment and thus are not prognostic of survival in the absence of treatment. In addition, we have 3 primary tumor datasets totaling 96 specimens with EGFR mutation information, thus providing a validation set for EGFR tyrosine kinase inhibitor signatures. Using a weighted voting classification, cell line signatures predicted drug response in primary tumors with accuracies of ∼65% for targeted therapy (EGFR) but with somewhat lower accuracies for platin/taxane therapies suggesting that cell line predictive signatures may be better suited for targeted drugs. To facilitate translation to clinical trials we are working with High Throughput Genomics (HTG) to develop quantitative mRNA profiles that are performed on formalin fixed paraffin embedded (FFPE) material on a platform that can be transferred to a CLIA certified environment. These studies thus provide a preclinical human tumor model platform for systematically testing new drugs and for developing signatures to guide their most efficient use in early clinical tests. Funded by University of Texas SPORE in Lung Cancer (P50CA70907) and NCI SPECS Lung Cancer (CA114771).

Citation Format: Luc Girard, Michael Peyton, Ignacio Wistuba, Yang Xie, Rachel Greer, Milind B. Suraokar, Carmen Behrens, Guanghua Xiao, John Heymach, David A. Wheeler, Caleb F. Davis, Kenneth Huffman, David S. Shames, Kevin R. Coombes, Adi F. Gazdar, David CL Lam, David G. Beer, John D. Minna. Molecular signatures of in vitro drug response in lung cancer. [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 5589. doi:10.1158/1538-7445.AM2013-5589

Elevated PDGFRB gene copy number gain as prognostic in resected malignant pleural mesothelioma

7078

Background: PDGF/PDGFR pathway has been implicated in malignant pleural mesothelioma (MPM) carcinogenesis. We sought to evaluate the incidence of PDGFRB gene copy number gain (CNG) and PDGFR pathway protein expression by immunohistochemistry (IHC) in the tumor cell cytoplasm, membrane, nucleus, and stroma, and correlate it to patient clinical outcome. Methods: 88 archived tumor blocks from resected MPM with full clinical information were used to perform the analyses. IHC biomarkers for PDGFRα,β and p-PDGFRβ, and fluorescence in situ hybridization were performed for analysis of PDGFRB gene CNG. Spearman’s rank correlation, Wilcoxon rank-sum test or Kruskal-Wallis test, BLiP plots, and Kaplan-Meier method were used to assess the biomarkers and their correlation to clinical outcome. Results: There were several correlations identified between the IHC biomarkers; however, none associated with patient demographics or histology subtype, with the exception of high cytoplasmic PDGFRα occurring in patients with no prior known asbestos exposure (p=0.029). In the CNG analysis, PDGFRB gene CNG in > 10% of tumor cells had lower cytoplasmic p-PDGFRβ (p=0.029), while PDGFRB gene CNG in > 40% of tumor cells had a higher cytoplasmic PDGFRβ (p=0.04). PDGFRB gene CNG status did not associate with patient demographics or tumor characteristics. Patients with PDGFRB CNG > 40% of tumor cells had an improved relapse-free survival (RFS) [HR 0.25 (95% CI 0.09, 0.72), p=0.0096]. In the patients with PDGFRB CNG > 40% of cells, the addition of chemotherapy appeared to also improve RFS (p=0.017). In the multi-covariate analyses for RFS, there was no association with any IHC biomarker. In the overall survival (OS) analysis, having PDGFRB gene CNG > 40% of tumor cells correlated with an improved OS [HR 0.32 (95% CI 0.11, 0.89), p=0.029] and the addition of peri-operative chemotherapy led to a trend towards improved OS (p=0.089). Conclusions: PDGFRB CNG > 40% of tumor cells is a potential prognostic biomarker in surgically resected MPM tumors. Adding chemotherapy to patients with PDGFRB CNG > 40% of cells improved RFS and led to a trend towards improved OS. Future validation of this biomarker in prospective trials is needed.

Abstract 3404: Exploring the role of Twist1 in the pathogenesis of malignant pleural mesothelioma (MPM)

Background: MPM is caused by lethal neoplastic growth of the pleura surrounding lungs. It is resistance to most standard anti-cancer treatment regimens and needs discovery of newer therapeutic approaches. MPM is characterized by massive loco-regional invasion of the malignant pleural cells into the lung parenchyma. Twist1 is a transcription factor, which promotes invasion and metastasis of tumor cells, increases chemotherapeutic resistance and is involved in the pathobiology of many cancers. Also recent studies have highlighted the potential of twist1 as a therapeutic target in cancer. But there is no report investigating its function in mesothelioma. Methods: We extracted total RNA from 53 frozen resected tumor tissue specimens, comprised of 39 epitheloid, 7 sarcomatoid and 7 biphasic histotypes, along with paired normal tissue. The RNA was labeled and hybridized to Affymetrix U133 plus 2.0 microarray to obtain transcriptomic profiles. Bioinformatic analysis of the microarray data using a 2 sample t-test was applied, on a probe-by-probe basis followed by Beta-uniform Mixture for multiple comparisons, to determine the differences between tumor vs normal specimens. The microarray results were validated by quantitative reverse transcriptase polymerase chain reaction (qRT-PCR) using Taqman assays on the ABI 7300 platform. For all qRT-PCR experiments the twist1 transcript levels were determined relative to endogenous GAPDH as control using ΔΔCT calculation. We performed Western blot analysis on a panel of 16 mesothelioma cell lines including Met-5A (SV-40 immortalized) and HCT-4012 (telomerase immortalized) pleural mesothelial control cell lines. Results: The bioinformatic analysis of microarray data showed that twist1 transcript level was 8.7 fold higher in tumors (p = 1.1E-16) compared to paired normal specimens. Using qRT-PCR, we compared twist1 transcript levels in 12 pairs of tumor vs paired normal tissue specimens and found that twist1 was upregulated to more than 10 fold in MPM tumors (p < E-4). Western blot showed that 10 MPM cancer cell lines had higher expression of twist1 protein compared to Met-5A and HCT-4012 cell lines. The highest expression was seen in 2 of the sarcomatoid cell lines - RS5 and DM3, suggesting a correlation with metastatic phenotype since sarcomatoid tumors are highly metastatic in nature. Conclusion: Our preliminary findings suggest that twist1 is upregulated in MPM tumors and cell lines and may play a role in the development of MPM. Further studies are needed to investigate its role in the process of tumorigenesis and metastasis. Supported by Grants: DoD W81XWH-07-1-0306 (I.I.W and AST), Fleming Foundation, IASLC Young Investigator Award 2011-2013 (MS).

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 3404. doi:1538-7445.AM2012-3404

Abstract 4031: CNG c-myc in mesothelioma

Background Malignant pleural mesothelioma (MPM) is a deadly disease with poor prognosis, few treatment options, and an increasing incidence worldwide. There is, therefore, a great need to identify new therapeutic targets and develop more effective therapies for patients with MPM. To better characterize the molecular changes occurring in MPM, we determined genetic and proteomic abnormalities in MPM cell lines and correlated them with those found in MPM tumor tissue specimens.

Methods We performed SNP/copy number analysis using Affymetrix SNP 6.0 chips, messenger RNA (mRNA) analysis using Affymetrix U133 plus 2.0 chips, and Reverse Protein Phase Array (RPPA) analysis in 4 mesothelioma cell lines (H28, MSTO-211H, H2052 and H2452) along with the control normal cell line HCT-4012, for comparison. DNA copy number microarray data were analyzed using the Nexus 5.0 software (BioDiscovery Inc.), while mRNA expression array data were analyzed using the GeneSpring GX 11 software (Agilent technologies, Inc.). Additionally, we evaluated copy number gain (CNG) of the c-myc gene and expression of c-myc protein in the mesothelioma cell lines and control cell line by fluorescent in situ hybridization (FISH) and Western blot, respectively. Furthermore, we investigated CGN in MPM tumor tissue specimens by performing FISH using the c-myc probe on tissue microarrays (TMAs) containing 80 MPM samples from different histological subtypes (41 epithelioid, 27 biphasic, 12 sarcomatoid).

Results DNA copy number analysis using the Affymetrix chip revealed CNG or amplification of the c-myc oncogenic locus in 3 out of 4 mesothelioma cell lines compared to the control HCT-4012 cell line. In concordance, the mRNA microarray data also showed increased number of transcripts from this locus; more importantly, the RPPA array data showed increased c-myc protein expression in these cell lines compared to control. These results were confirmed by FISH and Western blot analysis, which showed CNG or amplification at this locus and increased levels of the c-myc protein in the mesothelioma cell lines. FISH analysis of TMAs also revealed a relatively high frequency (21%) of CNG (≥4 copies in ≥70% of cells) for the c-myc locus in the MPM tumors. Interestingly, this amplification were seen in either epithelioid (10%) or biphasic (11%) histotype, and none were observed in the sarcomatoid cases. Similarly, within the biphasic cases, we observed that the amplification was present only in the epithelioid component, and not in the sarcomatoid component.

Conclusion Our findings suggest that CNG of the c-myc locus is characteristic for MPM tumors of the epithelioid histotype or of the epitheloid component of biphasic histotype, and suggest that c-myc CNG could have a role in pathogenesis of this disease; however, further studies are needed to clarify the role of c-myc in MPM development and progression. Supported by grant US DoD W81XWH-07-1-0306.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 4031. doi:10.1158/1538-7445.AM2011-4031

Abstract 4612: Cell-type dependent responses to selenium and knockdown of SBP2

Selenium is a trace element essential for human health. Evidence from previous epidemiologic studies and clinical trials suggested that selenium is associated with prostate cancer prevention, but its failure in the Selenium and Vitamin E Cancer Prevention Trial (SELECT) to reduce prostate cancer incidence diminished its promise. The question of whether some patients could benefit from selenium supplementation while others might not demands a clearer understanding of selenium's mechanisms of action. One of the ways in which selenium acts as a chemopreventive agent is through incorporation into selenoproteins, which are antioxidant enzymes required to maintain redox homeostasis; however, selenoproteins’ large number and redundant functions make analyzing their effects on cellular functions difficult. Therefore, we recently targeted selenocysteine insertion sequence-binding protein 2 (SBP2), required for selenoprotein synthesis; knocked down SBP2 expression in different cell lines; and examined the effect on cell survival, cell cycle, and cell survival pathways. We found that knocking down SBP2 resulted in apoptosis in NIH/3T3 and HEK-293 cells, especially in the presence of H2O2. Interestingly abrogation of SBP2 function affected the level of p21 protein in a cell type-specific manner. Additionally, sodium selenite or seleno-methionine treatment led to distinct changes in p21 and p53 protein status in HEK-293, LNCaP, and DU145 cells. Molecular effects induced by knocking down SBP2 were cell-type dependent. Further studies involving a combinational approach are expected to contribute to understanding how selenium and selenoproteins mediate chemopreventive effects in prostate cancer.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 4612. doi:10.1158/1538-7445.AM2011-4612

Abstract 2172: Deregulation of the mitotic spindle assembly checkpoint pathway in malignant pleural mesothelioma (MPM) tumors revealed by gene expression profiling

MPM is a lethal neoplasm exhibiting low median survival of patients and lacks effective therapeutic options. There is an urgent need to understand the underlying pathobiology and discover novel therapeutic targets. We undertook a messenger RNA (mRNA) expression profiling strategy to determine the pathways and biomarkers significantly altered in MPM tumors. We isolated total RNA from 55 MPM tumors with 38 paired controls representing 39 epitheloid, 8 biphasic and 6 sarcomatoid cases. The paired controls were adjacent non-tumor tissue samples and histopathological analysis revealed a tumor content of greater than 70 % in most of these tumors cases. The RNA was labeled and hybridized onto Affymetrix U133 Plus 2.0 chips to ascertain the global expression profile in these tumors.

Bioinformatic analysis of the microarray data using a two sample t-test was applied on a probe-by-probe basis followed by Beta-uniform Mixture for multiple comparisons. Finally paired t-test was applied to determine the differences between tumor vs normal samples. About ∼955 highly significant probesets representing ∼ 670 genes, at a FDR of e-09, were obtained and subjected to pathway analysis using MetaCore software suite (GeneGo, Inc.). The most significantly altered pathway in MPM tumors was the Mitotic Spindle Assembly Checkpoint (MSAC) pathway due to up-regulation of at least 15 genes including a ∼3.4 fold increase in Aurora kinase A, which is currently being explored in other cancers as a potential therapeutic target. The other genes belonging to this pathway, also up-regulated in tumors, include Mad2L1 and BUBR1 which together regulate cell division cycle 20 (Cdc20) protein, an essential cofactor needed by the Anaphase Promoting Complex to initiate the anaphase of cell cycle. Interestingly we also discovered that some of the MSAC pathway genes show a histotype-specific graded expression pattern with higher levels in sarcomatoid tumors compared to biphasic tumors and with lowest expression levels seen in epitheloid tumors. Additionally survivin, the product of which localizes to the mitotic spindle and negatively regulates apoptosis by inhibiting caspase activation, was expressed more than 2 fold in MPM tumors compared to normal samples. The microarray data also revealed other pathways significantly upregulated in MPM tumors including the Wnt and Cell-Adhesion signaling pathways. We are currently validating the expression microarray data using quantitative Polymerase Chain Reaction (PCR) platform with respect to key components of MSAC pathway. This will be followed by proteomic analysis of these components on tumor lysates to confirm the alterations in their expression profiles.

Supported by Grants: DOD PROSPECT W81XWH-07-1-030602, Fleming Foundation for Mesothelioma Research, Aileen Dillon and Lee Bourg Mesothelioma Endowment and NIH K12 CA088084 08 award.

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 2172.

p53 deficiency does not affect the accumulation of point mutations in a transgene target

DNA repair is required by organisms to prevent the accumulation of mutations and to maintain the integrity of genetic information. Mammalian cells that have been treated with agents that damage DNA have an increase in p53 levels, a p53-dependent arrest at G1 in the cell cycle, and a p53-dependent apoptotic response. It has been hypothesized that this block in cell cycle progression is necessary to allow time for DNA repair or to direct the damaged cell to an apoptotic pathway. This hypothesis predicts that p53-deficient cells would have an abnormal apoptotic response and exhibit a "mutator" phenotype. Using a sensitive assay for the accumulation of point mutations, small deletions, and insertions, we have directly tested whether p53-deficient cells exhibit an increased frequency of mutation before and after exposure to DNA-damaging agents. We report that wild-type and p53-deficient fibroblasts, thymocytes, and tumor tissue have indistinguishable rates of point mutation accumulation in a transgenic lacI target gene. These results suggest that the role of p53 in G1 checkpoint control and tumor suppression does not affect the accumulation of point mutations.