Detection of genetic alterations in gastric cancer patients from Saudi Arabia using comparative genomic hybridization (CGH).

BACKGROUND: The present study was conducted to discover genetic imbalances such as DNA copy number variations (CNVs) associated with gastric cancer (GC) and to examine their association with different genes involved in the process of gastric carcinogenesis in Saudi population. METHODS: Formalin-fixed paraffin-embedded (FFPE) tissues samples from 33 gastric cancer patients and 15 normal gastric samples were collected. Early and late stages GC samples were genotyped and CNVs were assessed by using Illumina HumanOmni1-Quad v.1.0 BeadChip. RESULTS: Copy number gains were more frequent than losses throughout all GC samples compared to normal tissue samples. The mean number of the altered chromosome per case was 64 for gains and 40 for losses, and the median aberration length was 679115bp for gains and 375889bp for losses. We identified 7 high copy gain, 52 gains, 14 losses, 32 homozygous losses, and 10 copy neutral LOHs (loss of heterozygosities). Copy number gains were frequently detected at 1p36.32, 1q12, 1q22, 2p11.1, 4q23-q25, 5p12-p11, 6p21.33, 9q12-q21.11, 12q11-q12, 14q32.33, 16p13.3, 17p13.1, 17q25.3, 19q13.32, and losses at 1p36.23, 1p36.32, 1p32.1, 1q44, 3q25.2, 6p22.1, 6p21.33, 8p11.22, 10q22.1, 12p11.22, 14q32.12 and 16q24.2. We also identified 2 monosomy at chromosome 14 and 22, 52 partially trisomy and 22 whole chromosome 4 neutral loss of heterozygosities at 13q14.2-q21.33, 5p15.2-p15.1, 5q11.2-q13.2, 5q33.1-q34 and 3p14.2-q13.12. Furthermore, 11 gains and 2 losses at 1p36.32 were detected for 11 different GC samples and this region has not been reported before in other populations. Statistical analysis confirms significant association of H. pylori infection with T4 stage of GC as compare to control and other stages. CONCLUSIONS: We found that high frequency of copy number gains and losses at 1p36.23, 1p32.1, 1p36.32, 3q25.2, 6p21.33 and 16q24.2 may be common events in gastric cancer. While novel CNVs at 1p36.32 harbouring PRDM16, TP73 and TP73-AS1 genes showed 11 gains and 2 losses for 11 different GC cases and this region is not reported yet in Database of Genomic Variants may be specific to Saudi population.

Detection and Genotyping of Helicobacter pylori among Gastric ulcer and Cancer Patients from Saudi Arabia.

BACKGROUND AND OBJECTIVES: Helicobacter pylori (H. pylori) infection is cause of several gastrointestinal diseases in humans. Virulence genes of H. pylori are associated with severity of disease and vary geographically. The aim of present study was to detect H. pylori in formalin-fixed paraffin-embedded (FFPE) tissues and further investigate prevalence of babA2, cagA, iceA1, iceA2, vacA s1/s2 and vacA m1/m2 genotypes in H. pylori from gastric cancer (GC) and gastric ulcer (GU) patients' biopsy samples. METHODS: We used FFPE tissues of 35 GC and 10 GU patients' biopsy samples. Using Polymerase Chain Reaction (PCR), detection of H. pylori strain was performed by using specific primers targeting 16S rRNA and ureC encodes for phosphoglucosamine mutase genes. We have identified different virulence genes of H. pylori by PCR. RESULTS: Of all the 45 samples tested, 20 GC and all 10 GU samples were positive for identification of H. pylori using specific genes (16S rRNA and ureC). The prevalence of babA2 (100%) was significantly higher in GC as compared to GU (40%) samples. The rate of virulence genes vacAs1 was higher in both GU 8 (80%) and GC (100%). CONCLUSIONS: Our study finds that vacAs1am1 and babA2 are most prominent genotypes and may play role in development of Gastric cancer.

microRNA analysis of gastric cancer patients from Saudi Arabian population.

BACKGROUND: The role of small non-coding microRNAs (miRNAs) in several types of cancer has been evident. However, its expression studies have never been performed in gastric cancer (GC) patients from Saudi population. First time this study was conducted to identify miRNAs that are differentially expressed in GC patients compared with normal controls. METHODS: We investigated the role of miRNAs in GC patients using formalin-fixed paraffin-embedded (FFPE) tissues of 34 samples from GC patients (early stage = 7 and late-stage = 26) and 15 from normal control. We have used miRNA microarray analysis and validated the results by Real-time quantitative PCR (RT-qPCR). RESULTS: We obtained data of 1082 expressed genes, from cancer tissues and noncancerous tissues (49 samples in total). Where 129 genes were up-regulated (P > 0.05) and 953 genes (P > 0.05) were down-regulated in 49 FFPE tissue samples. Only 33 miRNAs had significant expression in early and late-stage cancer tissues. After candidate miRNAs were selected, RT-qPCR further confirmed that four miRNAs (hsa-miR-200c-3p, hsa-miR-3613, hsa-miR-27b-3p, hsa-miR-4668-5p) were significantly aberrant in GC tissues compared to the normal gastric tissues. CONCLUSIONS: In this study we provide miRNAs profile of GC where many miRNAs showed aberrant expression from normal tissues, suggesting their involvement in the development and progression of gastric cancer. In early and late-stage miR-200c-3p showed significant down regulation as compare to control samples. Many of miRNAs reported in our study showing up-regulation are new and not reported before may be due to population difference. In conclusion, our results suggest that miR-200c-3p had potential to use as diagnostic biomarker for distinguishing GC patients from normal individuals and can be used for diagnosis of cancer at early stage.