Mehar Sultana

Prognostic significance of alterations in KRAS isoforms KRAS-4A/4B and KRAS mutations in colorectal carcinoma

Somatic KRAS mutation is an early well‐known event in colorectal carcinogenesis but a complete understanding of RAS function and dysfunction in colorectal cancer is still to come. Our aim was to study the incidence of KRAS mutation; KRAS splice variants: KRAS4A and KRAS4B; and their relationships with various clinico‐pathological characteristics in colorectal cancer (CRC).In this study, 285 CRC cases were analysed for KRAS mutation by direct DNA sequencing followed by immunohistochemical analysis after validation with real‐time PCR assay, to study the protein expression of KRAS4A and ‐4B isoforms. KRAS gene mutations were seen in 80/285 CRCs (28.1%) and of the mutated cases, the majority of the mutations were seen in codon 12 (81.2%) as opposed to codon 13 (18.8%). CRCs with KRAS mutations were associated with a poor overall survival (p = 0.0009). Furthermore, KRAS mutations at codon 12 were associated with a poor overall survival of 64.4% at 5 years compared with a 5‐year overall survival of 75.8% and 78.2% with codon 13 mutation and absence of KRAS mutations, respectively (p = 0.0025). KRAS4A protein expression was predominantly seen in the cytoplasm, while KRAS4B protein was nuclear. KRAS4A overexpression was significantly associated with left colon, histology subtype of adenocarcinoma, p27kip1, and cleaved caspase3 expression. Interestingly, KRAS4A overexpression was associated with a better overall survival (p = 0.0053). On the other hand, KRAS4B overexpression (33.2%) was significantly associated with larger tumour size (p = 0.0234) and inversely correlated with p27kip1 protein (p = 0.0159). Both KRAS mutation and KRAS4A were independent prognostic markers in a multivariate analysis with age, gender, stage, differentiation, and MSI status. Our results highlight the differential role of KRAS isoforms in CRC, their utility as a prognostic biomarker, and underline the importance of KRAS alterations as a potential therapeutic target for CRC. Copyright

Prognostic significance of XIAP expression in DLBCL and effect of its inhibition on AKT signalling

The inhibitor of apoptosis protein (IAP) family member X‐linked inhibitor of apoptosis protein (XIAP) is essential for cell survival in lymphoma. However, the role of XIAP overexpression in diffuse large B‐cell lymphoma (DLBCL) is not fully elucidated. Therefore, we analysed the expression of XIAP protein and its clinicopathological correlation in a large cohort of DLBCLs by immunohistochemistry in a tissue micro‐array format. XIAP was found to be overexpressed in 55% of DLBCLs and significantly associated with poor clinical outcome (p = 0.0421). To further elucidate the role of XIAP in DLBCL and the inter‐relationship with PI3‐kinase/AKT signalling, we conducted several in vitro studies using a panel of DLBCL cell lines. We found that pharmacological inhibition of XIAP led to caspase‐dependent apoptosis in DLBCL cells. We also detected an inter‐relationship between XIAP expression and activated AKT in DLBCL cells that may explain cellular resistance to PI3‐kinase/AKT inhibition‐mediated apoptosis. Finally, this anti‐apoptotic effect was overcome by simultaneous pharmacological inhibition of XIAP and PI3‐kinase/AKT signalling leading to a more potent synergistically induced apoptosis. In summary, our data suggest that XIAP expression is a poor prognostic factor in DLBCL and the XIAP‐AKT relationship should be explored further as a potential therapeutic target in DLBCL. Copyright

Frequent PIK3CA gene amplification and its clinical significance in colorectal cancer

Using a DNA microarray approach to screen for gene copy number changes in 20 colorectal (CR) carcinoma samples and filtering for high‐level DNA copy number changes, we detected an amplicon at 3q26 containing the PIK3CA gene. Fluorescence in situ hybridization was employed for evaluation of PIK3CA amplification on a progression CR tissue microarray containing 448 CR carcinomas, normal mucosa, and adenomas with follow‐up information. PIK3CA amplification (ratio PIK3CA/centromere 3≥2.0) was found in 38% of cancers, while another 19% of tumours had PIK3CA gains (ratio >1.0 but <2.0). Both PIK3CA amplification and gains were associated with high levels of PIK3CA protein expression and no association was seen between PIK3CA amplification and PIK3CA mutation. In a subset of 220 patients who received adjuvant chemotherapy and/or radiotherapy, survival in patients with PIK3CA‐amplified cancers was significantly longer compared with patients with cancers without amplification. This association was independent of stage, grade, histology subtype, gender, and age categories. Interestingly, PIK3CA amplification was also seen in CR adenomas, indicating an early genetic alteration, and was also a frequent event in colorectal carcinogenesis. Furthermore, PIK3CA amplification is an independent prognostic marker for better survival and may be one of the promising markers to define CRC subsets that may maximally benefit from adjuvant therapy. Copyright

Genome-wide expression analysis of Middle Eastern papillary thyroid cancer reveals c-MET as a novel target for cancer therapy†

In an attempt to find genes that may be of importance in malignant progression of papillary thyroid carcinoma (PTC) in the Middle East, which therefore can be targeted in cancer therapy, we screened and validated the global gene expression in PTC using cDNA expression arrays and immunohistochemistry (IHC) on tumour tissue microarrays. Twenty‐nine PTC tissue specimens were compared with seven non‐cancerous thyroid specimens by use of cDNA microarray. Results for selected genes were confirmed by quantitative real‐time PCR. Protein expression of selected genes was further studied using a tissue microarray consisting of 536 PTCs and compared with histologically non‐cancerous tissue samples. One hundred and ninety‐six genes were overexpressed in PTC tissues relative to non‐cancerous thyroid tissues. The genes that were up‐regulated in PTC were involved in cell cycle regulation, cell signaling, and oncogenesis. Among these genes, c‐MET was identified by immunohistochemical methods as a protein that is overexpressed in 37% of PTCs and was significantly associated with more aggressive behaviour, eg higher stage, nodal involvement, and tall cell variant (p value = 0.01, 0.01 and 0.04, respectively). In this study, 55% of the PTC cases expressed activated AKT (P‐AKT), which suggests that activated AKT may play an important role in PTC tumourigenesis. The fact that most of the PTC cases that had activated AKT showed overexpression of c‐MET (p = 0.027) leads us to hypothesize that c‐MET may be an alternative mechanism of AKT activation in Middle Eastern PTCs. Finally, our data suggest that c‐MET dysregulation is associated with aggressive behaviour and may serve as a molecular biomarker and potential therapeutic target in this disease. Copyright

Bortezomib Stabilizes Mitotic Cyclins and Prevents Cell Cycle Progression via Inhibition of UBE2C in Colorectal Carcinoma

Substantial evidence implicates the ubiquitin-conjugating enzyme E2C (UBE2C) gene, in several human cancers, including colorectal carcinoma (CRC). We therefore investigated the prognostic value of UBE2C alterations in CRC and UBE2C signaling in CRC cell lines. UBE2C protein expression and UBE2C gene copy number were evaluated on clinical samples by immunohistochemistry and fluorescence in situ hybridization in a TMA format. The effect of the proteasome inhibitor bortezomib and small-interfering RNA knockdown was assessed by apoptotic assays and immunoblotting. UBE2C dysregulation was associated with proliferative marker Ki-67, accumulation of cyclin A and B1, and a poor overall survival. UBE2C expression was an independent prognostic marker in early-stage (I and II) CRC. UBE2C depletion resulted in suppression of cellular growth and accumulation of cyclin A and B1. In vitro, bortezomib treatment of CRC cells caused inhibition of cell viability via down-regulation of UBE2C. UBE2C knockdown by bortezomib or transfection with specific small-interfering RNA against UBE2C also caused cells to be arrested at the G2/M level, leading to accumulation of cyclin A and cyclin B1. In vivo, a significant reduction in tumor volume and weight was noted in mice treated with a combination of subtoxic doses of oxaliplatin and bortezomib compared with treatment with oxaliplatin or bortezomib alone. Altogether, our results suggest that UBE2C and the ubiquitin-proteasome pathway may be potential targets for therapeutic intervention in CRC.

Distinct Gene Expression Profiles: Nodal versus Extranodal Diffuse Large B-Cell Lymphoma

Introduction: Approximately one third of diffuse large B-cell lymphomas (DLBCL) arises from tissues different from the lymph node. Perceived differences in outcome between extranodal and nodal DLBCL raise the possibility that these subgroups may represent different biological and clinical entities. Methods: Microarray GeneChip technology was used for global gene expression profiles from nodal (n = 19) and extranodal (n = 8) DLBCL, to examine possible differences between these subgroups. Quantitative RT-PCR was employed for validation of microarray data. Differential expression levels of p16 (CDKN2A) were confirmed by means of immunohistochemistry on a tissue microarray comprising more than 200 lymphoma samples. Results: A total of 218, over (124)- and underexpressed (94) genes were found to be differentially expressed in extranodal DLBCL compared with nodal DLBCL, including cytokines/chemokines, chromosome-replication-related genes and DNA repair genes. Quantitative RT-PCR confirmed the microarray data. A higher rate of p16 positivity was found in extranodal lymphomas. However, prognostic importance of p16 was associated with nodal rather than extranodal lymphomas. Conclusion: Our data suggest that a better distinction of these subgroups based on molecular classifiers is feasible and may greatly facilitate the determination of specific relevant clinical features and therapeutic implications of DLBCL with primary extranodal or nodal location.

colorectal cancer risk is not associated with increased levels of homozygosity in saudi Arabia

Purpose:Runs of homozygosity (ROHs) represent a measure of the extent of autozygosity and are correlated with the extent of inbreeding. Recently, it has been suggested that ROHs may contribute to the risk of colorectal cancer (CRC). The high rate of consanguinity and CRC in the Saudi population prompted us to test the role of autozygosity in the CRC risk.Methods:We compared 48 Saudi CRC patients to 100 ethnically matched controls, processed on the Affymetrix 250K StyI SNP GeneChip platform and analyzed using the plink package.Results:We could find no evidence of a significant relationship between autozygosity and CRC risk.Conclusion:The negative results in our study add additional significance to what has been previously reported in literature, as this is the first study to address these questions in an inbred population. Our subgroup analysis of patients with microsatellite unstable–positive tumors as compared with other groups did not significantly change our results. Although these results do not rule out the presence of recessively acting CRC-predisposing genes in a small percentage of patients, which our relatively small sample size could not capture, they suggest that such genes are unlikely to account for the disturbingly high incidence of CRC in our consanguineous population.Genet Med 2012:14(8):720–728

Abstract 110: Role of CARD 10 mediated NF-kB activation in colorectal carcinoma cells

Proceedings: AACR 103rd Annual Meeting 2012‐‐ Mar 31‐Apr 4, 2012; Chicago, IL Colorectal carcinoma is the fourth most common cancer in men and the third in women worldwide, accounting for 8% of all cancer deaths. NF-κB gene plays a role in tumorgenesis through the transcriptional activation of genes associated with cell proliferation, angiogenesis, metastasis, tumor promotion, inflammation and suppression of apoptosis. NF-κB protein activation, defined as nuclear expression of NF-κB by immunohistochemistry was an independent prognostic marker for poor survival. CARD10 gene is known positive regulator of the NF-κB activation pathway and can activate the NF-κB activity. CARD10 is an enzyme that is encoded by the CARD10 gene and it associates with IKK complex resulting in NF-κB activation. Considering the potential therapeutic utility of targeting NF-κB and its key modulators, we previously studied CARD10 genetic alterations and immunohistochemical expression of CARD10 in a large cohort cases1. CARD10 protein expression associated significantly with NF-κB activation, and CARD10 amplification was significantly associated with CARD10 protein expression and presence of distance metastasis. To extend and confirm our clinical finding, we performed in vitro studies using a panel of CRC cell lines to investigate the biological role of CARD10 alterations in CRC carcinogenesis. Our data showed that TNF-α treatment caused efficient translocation of p56 in CARD 10 muatation harboring cell line -DLD-1 cells to nucleus as compared to HCT-15 cells. Furthermore, the luciferase activity was significantly higher in CARD 10 amplified HCT-116 cells as compared to DLD1 and HCT-15 cells which carry normal CRAD10 gene copy number after 48 hours of transfection with an NF-κB reporter. In addition, it was also observed that the formation of colonies was significantly higher in HCT-116 as compared to DLD-1 and HCT-15. Finally CARD 10 siRNA transfection knocked down the expression of CARD10 and abrogated the expression of NF-κB, and resulted in apoptosis through activation of caspase-3. These data suggest that CARD10 mutation and amplification mediated NFκB activation play an important role in cellular transformation of CRC cells. Thus, the study raises the possibility that inhibition of CARD10 might have significant therapeutic value in CRC. Reference: 1: Jehad Abubaker, Prashant Bavi, Zeenath Jehan, Maqbool Ahmed, Wael Al-Haqawi, Mehar Sultana, Sarita Prabhakaran, Nasser Al-Sanea, Alaa Abduljabbar, Luai H Ashari, Samar Alhomoud, Fouad Al-Dayel, Shahab Uddin, Khawla S. Al-Kuraya. Clinicopathological significance of CARD10 alterations in Middle Eastern colorectal cancer. 102nd AACR Annual Meeting, April2-6, 2011, Orlando, Florida. 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 110. doi:1538-7445.AM2012-110

Abstract 1069: Clinicopathological significance of CARD10 alterations in Middle Eastern colorectal cancer

The incidence of Colorectal Carcinoma (CRC) in Saudi Arabia is rising and CRC is among the top 3 Saudi cancers in both men and women. NF-κB gene plays a role in tumorgenesis through the transcriptional activation of genes associated with cell proliferation, angiogenesis, metastasis, tumor promotion, inflammation and suppression of apoptosis. NF-κB protein activation, defined as nuclear expression of NF-kB by immunohistochemistry was seen in 43.2% (164/380) CRC and was an independent prognostic marker for poor survival. CARD10 and A20 genes are known positive and negative regulators of the NF-kB activation pathway and can activate the NF-kB activity. CARD10 is an enzyme that is encoded by the CARD10 gene and it associates with IKK complex resulting in NF-κB activation. CARD11 which shares a high degree of structure, domain and functional homology to CARD10 is oncogenic in diffuse large B cell lymphoma and results in activation of NF-κB. Considering the potential therapeutic utility of targeting NF-kB and its key modulators, we studied CARD10 genetic alterations (mutations and amplifications) and immunohistochemical expression of CARD10 in over 300 CRC cases and 13 colon cell lines. We detected missense mutations in 5.2 % (15/288) and 2 colon cell lines. Our results showed that CARD10 protein is widely expressed in CRC (67.7%) and expression levels of CARD10 progressively increase from normal colorectal mucosa to pre-malignant colorectal adenomas to CRC. CARD10 protein expression associated significantly with NF-KB activation (P = 0.0313). Interestingly, there was a mutual exclusivity between CARD10 protein overexpression and A20 loss of expression which might suggest that NFKB can be activated by alteration in one of these genes in CRC. Furthermore, CARD10 amplification (15.3%) was significantly associated with CARD10 protein expression and presence of distance metastasis (p=0.0487) Interestingly CARD10 mutations were detected in 21.4% of MSI CRC and only 78.6% of MSS CRC (p=0.0251), suggesting that CARD10 mutations play a role in both subsets of CRC but might represent more important oncogenic event for the development/progression of MSI CRC than MSS CRC. Our study highlights for the first time the role of CARD10 protein overexpression as a novel mechanism for NF-kB activation and demonstrates clinico-pathological significance of CARD10 alterations in Middle Eastern CRC. 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 1069. doi:10.1158/1538-7445.AM2011-1069

Abstract 3768: Colorectal cancer risk is not associated with increased levels of homozygosity in a population from Saudi Arabia

Proceedings: AACR 102nd Annual Meeting 2011‐‐ Apr 2‐6, 2011; Orlando, FL Autozygosity is a term used to denote the presence of two identical haplotypes that are derived from an ancestor shared by both parents, so it essentially represents a special type of homozygosity. Runs of homozygosity (ROH) in the genome is a measure of the extent of autozygosity and is directly correlated with the extent of inbreeding. While the role of ROH in unmasking recessively acting mutations is well established in Mendelian genetics, much less is known about their contribution to more complex disorders such as cancer. Recently, it has been suggested that ROH may contribute to the risk of colorectal cancer (CRC) perhaps through the unmasking of a recessively acting CRC-predisposing mutations in one or more genes. However, this observation could not be replicated. In this study, we examine the role of homozygosity in the CRC risk by asking four specific questions. First, do CRC patients have enrichment for ROH in particular chromosomal regions compared to controls? Second, do CRC patients have longer ROH compared to controls? Third, is there a particular SNP that is more likely to be homozygous in CRC patients compared to controls? And fourth, are CRC patients more inbred than controls? By comparing 48 Saudi CRC patients to 100 ethnically matched controls, all processed on Affy 250SytI SNP Chip platform and analyzed by Partek, we found that the answer is no to all these four questions. We note here that this is the first study to address these questions in an inbred population so the negative results in our study carry more significance than what has been previously reported in the literature. We also note that our subgroup analysis of patients with MSI-positive tumors compared to other groups did not significantly change our results. While these results do not rule out the potential presence of recessively acting CRC-predisposing genes in a small percentage of patients that our relatively small sample size could not capture, they do suggest that such genes are unlikely to account for the disturbingly high incidence of CRC in our consanguineous population and that future research should consider other mechanisms. 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 3768. doi:10.1158/1538-7445.AM2011-3768