Tumour suppressor properties of miR-15a and its regulatory effects on BCL2 and SOX2 proteins in colorectal carcinomas

OBJECTIVES

In this study, we aimed to investigate the expression pattern, clinicopathological significance and tumour suppressive properties of miR-15a in patients with colorectal carcinomas.

METHODS

Tissue samples from 87 patients with primary colorectal carcinomas, 50 matched metastatic lymph node and 37 non-neoplastic colon (control) were prospectively recruited. The expression level of miR-15a was measured by quantitative real-time polymerase chain reaction. Restoration/overexpression of the miR-15a was achieved by exogenous transfection. Four colon cancer cell lines (SW480, CaCO2, SW48 and HCT116) and a non-cancer colon cell line (FHC) were also used for examining the miR-15a induced tumour suppression properties using various in-vitro and immunological assays.

RESULTS

Downregulation of miR-15a was noted in ~ 62% of the colorectal carcinoma tissues and it was positively correlated with the presence of cancer recurrence in patients with colorectal carcinomas (p = 0.05). Also, these patients with low miR-15a expression showed relatively shorter survival time when compared to those with miR-15a overexpression. Following miR-15a exogenous overexpression, colon cancer cells showed reduced cell proliferation, low colony formation, less cell invasion properties and mitochondrial respiration when compared to control cells. In addition, BCL2 and SOX2 proteins showed a significant downregulation following miR-15a overexpression suggesting its regulatory role in cancer growth, apoptosis and stemness.

CONCLUSION

This study has confirmed the tumour suppressor properties of miR-15a in colorectal cancers. Therefore, its modulation has potential implications in controlling various biological and pathogenic processes in colon carcinogenesis via targeting its downstream proteins such as BCL2 and SOX2.

Targeted Single Gene Mutation in Esophageal Adenocarcinoma

Esophageal adenocarcinoma is heterogeneous and studies have reviewed many important mutations that contribute to the pathogenesis of the cancer. These discoveries have helped paved the way into identifying new gene markers or gene targets to develop novel molecular directed therapy for better patient outcomes in esophageal adenocarcinoma. Despite the recent bloom in next-generation sequencing, Sanger sequencing still represents the gold standard method for the study of the driver genes in esophageal adenocarcinoma. This chapter focuses on the sequencing techniques in identification of single gene mutations.

GAEC1 mutations and copy number aberration is associated with biological aggressiveness of colorectal cancer

GAEC1 (gene amplified in oesophageal cancer 1) is a transforming oncogene with tumorigenic potential observed in both oesophageal squamous cell carcinoma and colorectal cancer. Nonetheless, there has been a lack of study done on this gene to understand how this gene exert its oncogenic properties in cancer. This study aims to identify novel mutation sites in GAEC1. To do so, seventy-nine matched colorectal cancers were tested for GAEC1 mutation via Sanger sequencing. The mutations noted were investigated for the correlations with the clinicopathological parameters of the patients with the cancer. Additionally, GAEC1 copy number aberration (CNA), mRNA and protein expression were determined with the use of droplet digital (dd) polymerase chain reaction (PCR), real-time PCR and Western blot (confirmed with immunofluorescence analysis). GAEC1 mutation was noted in 8.8% (n = 7/79) of the cancer tissues including one missense mutation, four loss of heterozygosity (LOH) and two substitutions. These mutations were significantly associated with cancer perforation (p = 0.021). GAEC1 mutation is frequently associated with increased GAEC1 protein expression. Nevertheless, GAEC1 mRNA and protein are only weakly associated. Taken together, GAEC1 mutation affects GAEC1 expression and is associated with poorer clinical outcomes. This further strengthens the role of GAEC1 as an oncogene.

Promoter hypermethylation inactivate tumor suppressor FAM134B and is associated with poor prognosis in colorectal cancer

The present study aims to examine promoter methylation status of FAM134B in a large cohort of patients with colorectal adenocarcinomas. The clinical significances and correlations of FAM134B promoter methylation with its expression are also analysed. Methylation-specific high-resolution melt-curve analysis followed by sequencing was used to identify FAM134B promoter methylation in colorectal adenomas (N = 32), colorectal adenocarcinomas (N = 164), matched adjacent non-neoplastic colorectal mucosae (N = 83) and colon cancer cell lines (N = 4). FAM134B expression was studied by real-time quantitative polymerase chain reaction, immunohistochemistry, and Western blots. FAM134B promoter methylation was more frequent in adenocarcinomas (52%; 85/164) when compared to that of adenomas (28%; 9/32) and non-neoplastic mucosae (35%; 29/83). Cancer cells exhibited higher methylation when compared to non-neoplastic cells. FAM134B promoter methylation was inversely correlated with low FAM134B copy number and mRNA/protein expressions, whereas in-vitro demethylation has restored FAM134B expression in colon cancer cells. FAM134B promoter methylation was associated with high histological grade (P = .025), presence of peri-neural infiltration (P = .012), lymphovascular invasion (P = .021), lymph node metastasis (P = .0001), distant metastasis (P = .0001) and advanced pathological stages (P = .0001). In addition, FAM134B promoter methylation correlated with cancer recurrence and poor survival rates of patients with colorectal adenocarcinomas. To conclude, FAM134B promoter methylation plays a key role in regulating FAM134B expression in vitro and in vivo, which in turn contributes to the prediction of the biological aggressiveness of colorectal adenocarcinomas. Furthermore, FAM134B methylation might act as a marker in predicting clinical prognosis in patients with colorectal adenocarcinomas.

MiR-142-5p act as an oncogenic microRNA in colorectal cancer: Clinicopathological and functional insights

OBJECTIVES

miR-142-5p was noted aberrantly expressed and plays important roles in different pathophysiological conditions in human. The present study aims to examine the expression of miR-142-5p and its association with clinicopathological factors in a large cohort of patients with colorectal cancer. In addition, the cellular effects of miR-142-5p and its interacting targets in colon cancer cells were investigated.

METHODS

Expression of miR-142-5p in colorectal cancer tissues (n=125) and colon cancer cell lines were analysed using real-time polymerase chain reaction. In vitro assays (cell proliferation, wound healing and colony formation) were used to study the miR-142-5p induced cellular effects. Western blots were used to examine the modulation of FAM134B, KRAS, EPAS1 and KLF6 proteins expression followed by miR-142-5p expression-manipulation.

RESULTS

Significant high expression of miR-142-5p was noted in cancer tissues and cells when compared to the controls (p<0.001). Overexpression of miR-142-5p in patients with colorectal cancer was common (72%; 90/125). miR-142-5p overexpression was associated with cancer in the proximal colorectum and with B-raf positive patients (p=0.05). Exogenous overexpression of miR-142-5p resulted in significantly increased cell proliferation, colony formation, and wound healing capacities, whereas inhibition of endogenous miR-142-5p led reduced cancer growth properties. The cellular effects of miR-142-5p were mediated by the modulation of tumour suppressor KLF6 expression, as the expression of miR-142-5p and KLF6 protein are inversely correlated in colon cancer cells.

CONCLUSION

High miR-142-5p expression was associated with the biological aggressiveness of cancer. Thus, suppression of miR-142-5p could be a therapeutic strategy for patients with colorectal cancers.

Epigenetics: DNA Methylation Analysis in Esophageal Adenocarcinoma

The aberrant DNA methylation has been noted to occur at promoter of tumor suppressor, cell adhesion, DNA repair, and other growth regulating genes during the progression of nonneoplastic esophageal mucosa to Barrett esophagus to esophageal adenocarcinoma. Methylation-mediated silencing of individual gene or concurrent loss of a number of genes plays crucial roles in dysplasia-metaplasia-neoplasia sequence of esophageal adenocarcinoma. In addition, promoter methylation of genes had shown significant prognostic potential in patients with esophageal adenocarcinoma. Thus, determination of methylation status of genes of interest can be used as a molecular marker for risk stratification and/or better prognosis of patients with esophageal adenocarcinoma. There are a number of methods including bead array, PCR and sequencing, pyrosequencing, methylation-specific PCR, and PCR with high-resolution melt curve available to determine the methylation status of particular gene of interest. Herein, we describe the polymerase chain reaction followed by sequencing-based protocol for identifying DNA methylation status in esophageal adenocarcinoma.

Surface Markers for the Identification of Cancer Stem Cells

Cancer stem cells have genetic and functional characteristics that can turn them resistant to standard cancer therapeutic targets. Identification of these cells is challenging and is mostly done by detecting the expression of their antigens in a group of stem cells. Currently, there are a significant number of surface markers available which can detect the cancer stem cells by directly targeting their specific antigens present in cells. These markers possess differential expression patterns and sub-localizations in cancer stem cells when compared to non-neoplastic stem cells and somatic cells. In addition to molecular markers, multiple analytical methods and techniques including functional assays, cell sorting, filtration approaches, and xenotransplantation methods are used to identify cancer stem cells. This chapter will overview the functional significance of cancer stem cells, its biological correlations, specific markers, and detection methods.

Detection and Quantification of MicroRNAs in Esophageal Adenocarcinoma

MicroRNAs (miRNAs) are a class of small, noncoding RNAs that have been emerging as novel regulators in esophageal adenocarcinoma. Their role has been established in various aspects of esophageal adenocarcinoma including carcinogenesis, progression, treatment, and prognosis. Therefore, miRNA detection, profiling, and quantification have become extremely important for scientists and clinicians. As miRNAs are small, their detection can be challenging. There have been various methods developed to detect and/or quantify miRNAs. This chapter aims to introduce the fundamentals and methods of the most commonly used approaches including miRNA microarrays and quantitative real-time polymerase chain reaction (RT-qPCR) to detect and quantify miRNAs in esophageal adenocarcinoma.

RNA Interference-Mediated Gene Silencing in Esophageal Adenocarcinoma

RNA interference (RNAi) is a normal physiological mechanism in which a short effector antisense RNA molecule regulates target gene expression. It is a powerful tool to silence a particular gene of interest in a sequence-specific manner and can be used to target against various molecular pathways in esophageal adenocarcinoma by designing RNAi targeting key pathogenic genes. RNAi-based therapeutics against esophageal adenocarcinoma can be developed using different strategies including inhibition of overexpressed oncogenes, blocking cell division by interfering cyclins and related genes or enhancing apoptosis by suppressing anti-apoptotic genes. In addition, RNAi against multidrug resistance genes or chemo-resistance targets may provide promising cancer therapeutic options. Here, we describe RNAi technology using MET, a proto-oncogene in esophageal adenocarcinoma cells, as a model target. Lentiviral particles expressing MET shRNA was used to silence MET genes. Then, Western blot analysis was performed to confirm MET knockdown.

Identification of Cancer Stem Cells in Esophageal Adenocarcinoma

Cancer stem cells (CSCs) are a subpopulation of cancer cells that have the ability to self-renew and to generate differentiated cells of various lineages. Due to their specific morphological and biological features, they are often resistant to therapy and in turn lead to metastasis and cancer recurrence. Because of their crucial roles in carcinogenesis and patient prognosis, identification and isolation of CSCs have become an important part of improved cancer management regime. Isolation, characterization, and development of targeted therapy against CSCs have potential efficacy in treating esophageal cancer. In addition, CSCs can act as a predictive tool for chemoradiotherapy response in esophageal adenocarcinoma. Different methods including functional assays, cell sorting using various intracellular, and cell surface markers and xenotransplantation techniques are used for the identification and separation of CSCs in different cancers. None of these methods solely can guarantee complete isolation of CSC population, thus a combination of methods could be used for reliable detection and isolation of CSCs. Here, we describe the identification and isolation of CSCs from esophageal adenocarcinoma cells by cell sorting after Hoechst 33342 staining followed by in vitro functional assays, and in vivo xenograft techniques.

The clinical and biological roles of transforming growth factor beta in colon cancer stem cells: A systematic review

BACKGROUND

Transforming growth factor beta (TGF-β) is a multipurpose cytokine, which plays a role in many cellular functions such as proliferation, differentiation, migration, apoptosis, cell adhesion and regulation of epithelial to mesenchymal transition. Despite many studies having observed the effect that TGF-β plays in colorectal cancer, its role in the colorectal stem cell population has not been widely observed.

METHOD

This systematic review will analyse the role of TGF-β in the stem cell population of colorectal cancer.

RESULTS

The effects on the stem cell phenotype are through the downstream proteins involved in activation of the TGF-β pathway. Its involvement in the initiation of the epithelial to mesenchymal transition (EMT), the effect of colorectal invasion and metastasis regulated through the Smad protein involvement in the EMT, initiation of angiogenesis, promotion of metastasis of colorectal cancer to the liver and its ability to cross-talk with other pathways.

CONCLUSION

TGF-β is a key player in angiogenesis, tumour growth and metastasis in colon cancer.

Clinical and biological significance of miR-193a-3p targeted KRAS in colorectal cancer pathogenesis

This study was to investigate the expression pattern, mechanisms and clinicopathological implications of miR-193a-3p in colorectal cancer. Fresh-frozen tissues from 70 matched colorectal adenocarciomas and the adjacent non-neoplastic mucosae were prospectively collected. Two colorectal cancer cell lines (SW480 and SW48) and a non-neoplastic colon cell line (FHC) were also used. The expression levels of miR193a-3p in the cells and tissues were measured by quantitative real-time polymerase chain reaction. The expression of KRAS protein as a predicted downstream target for miR-193a was studied by immunohistochemistry. Restoration of the miR-193a level in the cell lines by permanent transfection was achieved and multiple functional and immunological assays were performed to analyze the functions of miR-193a in vitro. Down-regulation of miR-193a-3p was noted in 70% of the colorectal cancer tissues when compared to non-neoplastic colorectal tissues. In addition, down-regulation of miR-193a was significantly correlated with carcinoma of early stages (P<.05). Significant inverse correlation between miR-193a-3p and its target KRAS protein was determined (P<.05). Overexpression of miR-193a in colon cancer cells resulted in reduced cell proliferation, increased apoptosis, induced significant changes in cell cycle events and decreased the expression of epithelial-mesenchymal transition marker TWIST. This study confirms the tumor suppressor roles of miR-193a-3p, its downstream target affinity to KRAS and clinical significance in patients with colorectal adenocarcinoma.

The roles of microRNA-34b-5p in angiogenesis of thyroid carcinoma

PURPOSE

This study aims to determine the expression of miR-34b-5p in thyroid carcinomas and to investigate the role of miR34b-5p in the modulation of proteins involved in angiogenesis of thyroid carcinoma cells.

METHODS

The expressions of miR-34b-5p levels in five cell lines and 65 tissue samples from thyroid carcinomas were examined by real-time polymerase chain reaction. An exogenous miR-34b-5p (mimic) transiently overexpress miR-34b-5p in theses thyroid carcinoma cells. The effects of miR-34b-5p overexpression on the proteins involved in angiogenesis and cell cycle regulations (VEGF-A, Bcl-2 and Notch1) were investigated by Western blot, immunofluorescence, enzyme-linked immunosorbent assay followed by cell cycle analysis and apoptosis assays.

RESULTS

miR-34b-5p is markedly downregulated in all thyroid carcinoma cell lines and tissues samples when compared with non-neoplastic immortalised thyroid cell line and non-neoplastic thyroid tissues, respectively. The expression levels of miR-34b were significantly associated with T-stages of thyroid carcinomas (p = 0.042). Downregulation of VEGF-A, Bcl-2 and Notch1 proteins in thyroid carcinoma cells were noted in cells that transiently transfected with miR-34b-5p mimic. In addition, enzyme-linked immunosorbent assay confirmed the decreased expression of VEGF in thyroid carcinoma cells after transfection with miR-34b-5p mimic. Furthermore, miR-34b-5p mimic transfection induces significant accumulation of cells in G0-G1 of the cell cycle by blocking of their entry into the S transitional phase as well as increasing the total apoptosis.

CONCLUSIONS

miR-34b-5p functions as a potent regulator of angiogenesis, apoptosis and cell proliferation via modulation of VEGF-A, Bcl-2 and Notch1 proteins. It could be a target for developing treatment strategies of thyroid carcinoma with aggressive clinical behaviour.

Correction: Gold-loaded nanoporous iron oxide nanocubes: a novel dispersible capture agent for tumor-associated autoantibody analysis in serum

Correction for 'Gold-loaded nanoporous iron oxide nanocubes: a novel dispersible capture agent for tumor-associated autoantibody analysis in serum' by Sharda Yadav et al., Nanoscale, 2017, 9, 8805-8814.

Gold-loaded nanoporous ferric oxide nanocubes for electrocatalytic detection of microRNA at attomolar level

A crucial issue in microRNA (miRNA) detection is the lack of sensitive method capable of detecting the low levels of miRNA in RNA samples. Herein, we present a sensitive and specific method for the electrocatalytic detection of miR-107 using gold-loaded nanoporous superparamagnetic iron oxide nanocubes (Au-NPFe₂O₃NC). The target miRNA was directly adsorbed onto the gold surfaces of Au-NPFe₂O₃NC via gold-RNA affinity interaction. The electrocatalytic activity of Au-NPFe₂O₃NC was then used for the reduction of ruthenium hexaammine(III) chloride (RuHex, [Ru(NH₃)₆]³⁺) bound with target miRNA. The catalytic signal was further amplified by using the ferri/ferrocyanide [Fe(CN)₆]^3-/4- system. These multiple signal enhancement steps enable our assay to achieve the detection limit of 100aM which is several orders of magnitudes better than most of the conventional miRNA sensors. The method was also successfully applied to detect miR-107 from cancer cell lines and a panel of tissue samples derived from patients with oesophageal squamous cell carcinoma with excellent reproducibility (% RSD = < 5%, for n = 3) and high specificity. The analytical accuracy of the method was validated with a standard RT-qPCR method. We believe that our method has the high translational potential for screening miRNAs in clinical samples.

ID: 1036 FAM134B, a new player in human colorectal cancer pathogenesis

Background: FAM134B (family with sequence similarity 134, member B) is a relatively new player in many human diseases including cancers. In colorectal carcinomas, FAM134B plays important role in the pathogenesis and associated with biological aggressiveness of the disease. However, expression pattern, the frequency of mutations, methylation status in colon cancer cells and tissue samples has never been studied. Also, the functional roles of FAM134B in cell have never been studied in colorectal cancer. Objectives: To investigate FAM134B promoter methylation, mutations in tissues samples from patients with colorectal cancer and cell lines. Also, promoter methylation, expression and functional roles of FAM134B in colon cancer were studied.  Methods: Methylation and mutations in FAM134B sequence in cancer tissues (n=126) and matched non-cancer samples was studied by high-resolution melt curve analysis followed by Sanger sequencing. FAM134B expression was studied and quantified in cell lines and cancer tissues samples using immunofluorescence, immunocytochemistry, Western blot and real time PCR. In vitro functional assays and mouse xenotransplantation model were performed to unveil the molecular roles of FAM134B in colon cancer pathogenesis followed by shRNA-mediated silencing in cells.  Results: We noted that 46.5% (41/88) patients with colorectal cancer were identified as FAM134B mutations positive. Thirty-one novel pathogenic mutations were detected and these mutations were associated with gender of the patients, presence of metachronous cancer, size, T staging, presence of distant metastases and positivity of microsatellite instability (MSI) in the cancer (p < 0.05). Majority of cancer tissues had shown promoter hyper-methylation and were correlated with reduced mRNA and protein expression in both cancer samples and cells. FAM134B expression in cancer cells derived from advanced stages (stage III; SW48 and stage IV; HCT116) of colon cancer was significantly (p<0.01) reduced when compared to non-neoplastic colon cells (FHC) and cancer cells derived from stage II colon cancer (SW480). Expression of FAM134B mRNA in cancer tissues was noted significantly (p<0.001) downregulated when compared to that of non-cancer tissues samples. FAM134B suppression significantly (p<0.05) increased the proliferation of colon cancer cells, remarkably increased (3452% ; p<0.05) the clonogenic, migration capacity, and increases the proportion of cells in S phase of cell cycle (p<0.01). Xenotransplantation model showed that larger and higher grade tumors were formed in mice treated with FAM134B knockdown cells. Conclusion: Reduced expression in cancer samples, in vitro and in vivo functional studies implied that FAM134B acts as a cancer inhibitor in colon cancer play important roles in colorectal carcinogenesis.

Cellular expression, in-vitro and in-vivo confirmation of GAEC1 oncogenic properties in colon cancer

GAEC1 (Gene amplified in esophageal cancer 1) alterations have oncogenic properties in oesophageal squamous cell carcinomas and frequent amplifications of the gene were noted in colorectal adenocarcinomas. However, the subcellular localization and expression of GAEC1 at the protein level have never been reported in human cancer cells. The present study aimed to investigate whether GAEC1 is differentially expressed in different stages of colon cancer and to elucidate its underlying cellular and molecular mechanism in colon cancer progression. We found differential expression of GAEC1 protein and mRNA in different pathological stages of colon cancer cells (SW480-Stage II, SW48-Stage III and HCT116-Stage IV) when compared to non-neoplastic colon cells (FHC cells) by immunocytochemistry, immunofluorescence, western blot analysis and real-time polymerase chain reaction. GAEC1 protein was predominantly expressed in the cytoplasm of colon cancer cells (SW480, SW48, and HCT116) and in the nucleus of non-neoplastic colon epithelial cells (FHC cells). The transient knockdown of GAEC1 using siRNA induced apoptosis in SW480 and SW48 cells, which was associated with G2/M phase arrest and decreased expression of bcl-2 and K-ras proteins and increased expression of p53. In addition, down-regulation of GAEC1 significantly inhibited (p<0.05) cell proliferation, reduced migration capacity and decreased clonogenic potentiality of colon cancer cells (SW480 and SW48 cells). Furthermore, a xenotransplantation model showed that stable knockdown of GAEC1 using shRNA constructs in colon cancer cells fully suppressed xenograft tumour growth in mice. Collectively, the expression analysis, in vitro and in vivo data indicated that GAEC1 is differentially expressed in cancer cells and act as an oncogene in colon cancer progression.

Whole-exome sequencing reveals critical genes underlying metastasis in oesophageal squamous cell carcinoma

Oesophageal squamous cell carcinoma (ESCC) is one of the most lethal cancers, owing to a high frequency of metastasis. However, little is known about the genomic landscape of metastatic ESCC. To identify the genetic alterations that underlie ESCC metastasis, whole-exome sequencing was performed for 41 primary tumours and 15 lymph nodes (LNs) with metastatic ESCCs. Eleven cases included matched primary tumours, synchronous LN metastases, and non-neoplastic mucosa. Approximately 50-76% of the mutations identified in primary tumours appeared in the synchronous LN metastases. Metastatic ESCCs harbour frequent mutations of TP53, KMT2D, ZNF750, and IRF5. Importantly, ZNF750 was recurrently mutated in metastatic ESCC. Combined analysis from current and previous genomic ESCC studies indicated more frequent ZNF750 mutation in diagnosed cases with LN metastasis than in those without metastasis (14% versus 3.4%, n = 629, P = 1.78 × 10^-5 ). The Cancer Genome Atlas data further showed that ZNF750 genetic alterations were associated with early disease relapse. Previous ESCC studies have demonstrated that ZNF750 knockdown strongly promotes proliferation, migration, and invasion. Collectively, these results suggest a role for ZNF750 as a metastasis suppressor. TP53 is highly mutated in ESCC, and missense mutations are associated with poor overall survival, independently of pathological stage, suggesting that these missense mutations have important functional impacts on tumour progression, and are thus likely to be gain-of-function (GOF) mutations. Additionally, mutations of epigenetic regulators, including KMT2D, TET2, and KAT2A, and chromosomal 6p22 and 11q23 deletions of histone variants, which are important for nucleosome assembly, were detected in 80% of LN metastases. Our study highlights the important role of critical genetic events including ZNF750 mutations, TP53 putative GOF mutations and nucleosome disorganization caused by genetic lesions seen with ESCC metastasis. Copyright © 2017 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Abstract 3420: Mutational status, expression and functional behaviors of FAM134B in colorectal cancer

Background: Family with sequence similarity 134B (FAM134B) is an ER-autophagy regulator and involved in the pathogenesis of neuronal disorders, vascular diseases and carcinomas. In colorectal carcinomas, FAM134B plays important role in the pathogenesis and associated with aggressiveness of the disease. However, the frequency of mutations, expression pattern and functional roles in cell have never been studied in colorectal cancer.

Objectives: To investigate FAM134B mutations in tissues samples from patients with colorectal cancer and cell lines. Also, the expression of FAM134B at protein and mRNA levels were examined. In addition, functional roles of FAM134B in colon cancer were studied.

Methods: Mutations in FAM134B sequence in eighty-eight cancer tissues and matched non-cancer samples was studied by high-resolution melt curve analysis followed by Sanger sequencing. FAM134B expression was studied and quantified in cell lines and cancer tissues samples using immunofluorescence, immunocytochemistry, Western blot and real-time PCR. In vitro functional assays were performed to unveil the molecular roles of FAM134B in colon cancer pathogenesis followed by shRNA-mediated silencing in cells. Mouse xenotransplantation model was used to confirm the functional behavior of FAM134B in colon cancer.

Results: In this study, 46.5% (41/88) patients with colorectal cancer were identified as FAM134B mutations positive. Thirty-one novel pathogenic mutations were detected. Of the 31 mutations, 8 novel frameshift mutations caused nonsense-mediated mRNA decay and associated with gender of the patients, presence of metachronous cancer, size, T staging, presence of distant metastases and positivity of microsatellite instability (MSI) in the cancer (p &lt; 0.05). FAM134B expression in cancer cells derived from advanced stages (stage III; SW48 and stage IV; HCT116) of colon cancer was significantly (p&lt;0.01) reduced when compared to non-neoplastic colon cells (FHC) and cancer cells derived from stage II colon cancer (SW480). Expression of FAM134B mRNA in cancer tissues was noted significantly (p&lt;0.001) downregulated when compared to that of non-cancer tissues samples. FAM134B suppression significantly (p&lt;0.05) increased the proliferation of colon cancer cells, remarkably increased (34-52%; p&lt;0.05) the clonogenic, migration capacity, and increases the proportion of cells in S phase of cell-cycle (p&lt;0.01). Xenotransplantation model showed that larger and higher-grade tumors were formed in mice treated with FAM134B knockdown cells.

Conclusion: In vitro and in vivo functional studies implied that FAM134B acts as a cancer inhibitor in colon cancer. Also, FAM134B mutation is common in colorectal cancer and the association of mutation with adverse clinical and pathological parameters are in concur with the tumour suppressive property of the gene.

Note: This abstract was not presented at the meeting.

Citation Format: Farhadul Islam, Vinod Gopalan, Riajul Wahab, Katherine Ting-wei Lee, Afraa Mamoori, Cu-tai Lu, Robert A Smith, Alfred K-Y Lam. Mutational status, expression and functional behaviors of FAM134B in colorectal cancer [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 3420. doi:10.1158/1538-7445.AM2017-3420

Abstract 1243: FAM134B mutation in esophageal squamous cell carcinoma: Its clinical significance and quantification by electrochemical methods

Aim: The aim of this research was to detect novel sites of FAM134B mutations, copy number variations and their clinicopathological significance in esophageal squamous cell carcinoma (ESCC) patients. Also, this study was intended to develop a simple and inexpensive electrochemical detection method for the analysis of FAM134B mutations using a single-use and disposable screen-printed electrode.

Method: Approximately 102 fresh tissue samples of ESCC and matched non-cancer adjacent tissues were recruited. The DNA copy numbers of FAM134B were initially studied by qRT-PCR. The FAM134B mutations were then quantified via high resolution melt curve (HRM) and Sanger sequencing analysis. In order to quantify the level of point mutation or SNPs in FAM134B gene, a new electrochemical method was also developed. The underlying working principle of the method is relied on the base dependent affinity interactions towards gold electrode. Since two DNA sequences with different DNA base compositions (i.e., amplified mutated sequences will be distinctly different than its wild type sequence) will have different adsorption affinity towards an unmodified gold electrode, accurate measurement of adsorbed DNA on the electrode surface will give the measure of point mutation or SNPs present in the DNA sequences. Target DNA sequences were first extracted from clinical samples and then PCR amplified and purified prior to adsorption on a single-use screen-printed gold electrode. The amount of mutation sites on a DNA sequence is quantified by monitoring the Faradaic current generated by the [Fe(CN)6]3-/4- system present in the electrolyte solution.

Result: Amplification of FAM134B DNA was noted in 37% of ESCC tissues whereas 35% cases showed loss of FAM134B copies compared to matched non-tumor tissues. Overall, thirty-seven FAM134B mutations were documented in exons 4, 5, 7, 9 as well as introns 2, 4-8 of FAM134B. Also, FAM134B mutations were detected in all the metastatic ESCC cases and in 14% (8/57) of the primary ESCC. Using the new electrochemical method, we were able to detect mutations in 50 ng of target PCR-amplified product within 1 h with high reproducibility (% RSD= &lt;2) and specificity.

Conclusion: DNA copy number variations and frequent mutations of FAM134B in metastatic lymph node tissues in ESCC patients indicate its critical role in the pathogenesis of ESCCs. Also the mutation detection via electrochemical methods was successful distinguishing single point mutation in DNA from oesophageal cancer implying its potential application in point mutation detection in clinical diagnostics.

Note: This abstract was not presented at the meeting.

Citation Format: Md. Hakimul Haque, Vinod Gopalan, Muhammad J. A. Shiddiky, Alfred K. Lam. FAM134B mutation in esophageal squamous cell carcinoma: Its clinical significance and quantification by electrochemical methods [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 1243. doi:10.1158/1538-7445.AM2017-1243

Abstract 2150: Oncogenic role of GAEC1 and its potential modulation with p53 in pathogenesis of colon cancer

Introduction: GAEC1 (Gene amplified in esophageal cancer 1), is frequently amplified and overexpressed in colon cancer tissues. In the present study, we aimed to unveil the oncogenic potential of GAEC1 in carcinogenesis of colon cancer by studying the underlying cellular functions and molecular interactions by in vitro and in vivo experiments.

Method: Transient overexpression of GAEC1 with pcDNA3.1-GAEC1 and silencing with GAEC1-siRNA was performed and several downstream assays were done such as migration, clonogenic and apoptotic assay. Analysis of cell kinetics was done using flow cytometry and cell counting kit-8 was used for cell proliferation assay. Immunofluorescence and Western blot assay were used to determine the expression of different target proteins. Co-immunoprecipitation was used to confirm the protein-protein interaction. For xenotransplantation the severely combined immunodeficient (SCID) mice (4 groups, 6 in each group) were injected subcutaneously with GAEC1 shRNA and control shRNA transfected (stable) SW480 and SW48 colon cancer cells.

Result: The overexpression of GAEC1 increased cell proliferation, migration, reduced apoptosis in colon cancer cells. Also, these cells showed cell cycle arrest at the synthetic phase, activation of Bcl-2, K-ras, pAKT proteins as well as inhibition of p53, PUMA, p21 and BAX proteins. Conversely, knockdown of GAEC1 reduced cell proliferation, migration, decreased the phosphorylation of AKT, and induced apoptosis, G2/M phase arrest and cleavage of poly (ADP-ribose) polymerase (PARP). Co-immunoprecipitation revealed GAEC1’s interaction with p53. In addition ectopic over expression and silencing of GAEC1 lead to reciprocal effects of p53 protein expression. Moreover, knockdown of GAEC1 reduced the nuclear translocation of murine double minute 2 protein (mdm2) indicating that GAEC1 is responsible for the degradation of p53 through the direct interaction between mdm2-p53 in nucleus. Furthermore, our in vivo data demonstrate that the loss of GAEC1 inhibits the tumor formation in xenograft model.

Conclusion: Collectively our study demonstrates that GAEC1 exhibits the oncogenic role in colon cancer by reducing expression of p53 through protein-protein interaction which leads to the inhibition of PUMA, p21, BAX, and activation of Bcl-2, K-ras and pAKT protein expression.

Note: This abstract was not presented at the meeting.

Citation Format: Riajul Wahab, Farhadul Islam, Vinod Gopalan, Alfred King-Yin Lam. Oncogenic role of GAEC1 and its potential modulation with p53 in pathogenesis of colon cancer [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 2150. doi:10.1158/1538-7445.AM2017-2150

Abstract 5764: Oncogenic role of GAEC1 and its potential modulation with p53 in pathogenesis of colon cancer

Introduction: GAEC1 (Gene amplified in esophageal cancer 1), is frequently amplified and overexpressed in colon cancer tissues. In the present study, we aimed to unveil the oncogenic potential of GAEC1 in carcinogenesis of colon cancer by studying the underlying cellular functions and molecular interactions by in vitro and in vivo experiments.

Method: Transient overexpression of GAEC1 with pcDNA3.1-GAEC1 and silencing with GAEC1-siRNA was performed and several downstream assays were done such as migration, clonogenic and apoptotic assay. Analysis of cell kinetics was done using flow cytometry and cell counting kit-8 was used for cell proliferation assay. Immunofluorescence and Western blot assay were used to determine the expression of different target proteins. Co-immunoprecipitation was used to confirm the protein-protein interaction. For xenotransplantation the severely combined immunodeficient (SCID) mice (4 groups, 6 in each group) were injected subcutaneously with GAEC1 shRNA and control shRNA transfected (stable) SW480 and SW48 colon cancer cells.

Result: The overexpression of GAEC1 increased cell proliferation, migration, reduced apoptosis in colon cancer cells. Also, these cells showed cell cycle arrest at the synthetic phase, activation of Bcl-2, K-ras, pAKT proteins as well as inhibition of p53, PUMA, p21 and BAX proteins. Conversely, knockdown of GAEC1 reduced cell proliferation, migration, decreased the phosphorylation of AKT, and induced apoptosis, G2/M phase arrest and cleavage of poly (ADP-ribose) polymerase (PARP). Co-immunoprecipitation revealed GAEC1’s interaction with p53. In addition ectopic over expression and silencing of GAEC1 lead to reciprocal effects of p53 protein expression. Moreover, knockdown of GAEC1 reduced the nuclear translocation of murine double minute 2 protein (mdm2) indicating that GAEC1 is responsible for the degradation of p53 through the direct interaction between mdm2-p53 in nucleus. Furthermore, our in vivo data demonstrate that the loss of GAEC1 inhibits the tumor formation in xenograft model.

Conclusion: Collectively our study demonstrates that GAEC1 exhibits the oncogenic role in colon cancer by reducing expression of p53 through protein-protein interaction which leads to the inhibition of PUMA, p21, BAX, and activation of Bcl-2, K-ras and pAKT protein expression.

Note: This abstract was not presented at the meeting.

Citation Format: Riajul Wahab, Farhadul Islam, Vinod Gopalan, Alfred King-Yin Lam. Oncogenic role of GAEC1 and its potential modulation with p53 in pathogenesis of colon cancer [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 5764. doi:10.1158/1538-7445.AM2017-5764