André Salim Khayat

Ultra-Deep Sequencing Reveals the microRNA Expression Pattern of the Human Stomach

Background While microRNAs (miRNAs) play important roles in tissue differentiation and in maintaining basal physiology, little is known about the miRNA expression levels in stomach tissue. Alterations in the miRNA profile can lead to cell deregulation, which can induce neoplasia. Methodology/Principal Findings A small RNA library of stomach tissue was sequenced using high-throughput SOLiD sequencing technology. We obtained 261,274 quality reads with perfect matches to the human miRnome, and 42% of known miRNAs were identified. Digital Gene Expression profiling (DGE) was performed based on read abundance and showed that fifteen miRNAs were highly expressed in gastric tissue. Subsequently, the expression of these miRNAs was validated in 10 healthy individuals by RT-PCR showed a significant correlation of 83.97% (P<0.05). Six miRNAs showed a low variable pattern of expression (miR-29b, miR-29c, miR-19b, miR-31, miR-148a, miR-451) and could be considered part of the expression pattern of the healthy gastric tissue. Conclusions/Significance This study aimed to validate normal miRNA profiles of human gastric tissue to establish a reference profile for healthy individuals. Determining the regulatory processes acting in the stomach will be important in the fight against gastric cancer, which is the second-leading cause of cancer mortality worldwide.

MYC, FBXW7 and TP53 copy number variation and expression in Gastric Cancer

BackgroundMYC deregulation is a common event in gastric carcinogenesis, usually as a consequence of gene amplification, chromosomal translocations, or posttranslational mechanisms. FBXW7 is a p53-controlled tumor-suppressor that plays a role in the regulation of cell cycle exit and reentry via MYC degradation.MethodsWe evaluated MYC, FBXW7, and TP53 copy number, mRNA levels, and protein expression in gastric cancer and paired non-neoplastic specimens from 33 patients and also in gastric adenocarcinoma cell lines. We also determined the invasion potential of the gastric cancer cell lines.ResultsMYC amplification was observed in 51.5% of gastric tumor samples. Deletion of one copy of FBXW7 and TP53 was observed in 45.5% and 21.2% of gastric tumors, respectively. MYC mRNA expression was significantly higher in tumors than in non-neoplastic samples. FBXW7 and TP53 mRNA expression was markedly lower in tumors than in paired non-neoplastic specimens. Moreover, deregulated MYC and FBXW7 mRNA expression was associated with the presence of lymph node metastasis and tumor stage III-IV. Additionally, MYC immunostaining was more frequently observed in intestinal-type than diffuse-type gastric cancers and was associated with MYC mRNA expression. In vitro studies showed that increased MYC and reduced FBXW7 expression is associated with a more invasive phenotype in gastric cancer cell lines. This result encouraged us to investigate the activity of the gelatinases MMP-2 and MMP-9 in both cell lines. Both gelatinases are synthesized predominantly by stromal cells rather than cancer cells, and it has been proposed that both contribute to cancer progression. We observed a significant increase in MMP-9 activity in ACP02 compared with ACP03 cells. These results confirmed that ACP02 cells have greater invasion capability than ACP03 cells.ConclusionIn conclusion, FBXW7 and MYC mRNA may play a role in aggressive biologic behavior of gastric cancer cells and may be a useful indicator of poor prognosis. Furthermore, MYC is a candidate target for new therapies against gastric cancer.

Prognostic and Predictive Significance of MYC and KRAS Alterations in Breast Cancer from Women Treated with Neoadjuvant Chemotherapy

Breast cancer is a complex disease, with heterogeneous clinical evolution. Several analyses have been performed to identify the risk factors for breast cancer progression and the patients who respond best to a specific treatment. We aimed to evaluate whether the hormone receptor expression, HER2 and MYC genes and their protein status, and KRAS codon 12 mutations may be prognostic or predictive biomarkers of breast cancer. Protein, gene and mutation status were concomitantly evaluated in 116 breast tumors from women who underwent neoadjuvant chemotherapy with doxorubicin plus cyclophosphamide. We observed that MYC expression was associated with luminal B and HER2 overexpression phenotypes compared to luminal A (p<0.05). The presence of MYC duplication or polysomy 8, as well as KRAS mutation, were also associated with the HER2 overexpression subtype (p<0.05). MYC expression and MYC gain were more frequently observed in early-onset compared to late-onset tumors (p<0.05). KRAS mutation was a risk factor of grade 3 tumors (p<0.05). A multivariate logistic regression demonstrated that MYC amplification defined as MYC/nucleus ratio of ≥2.5 was a protective factor for chemotherapy resistance. On the other hand, age and grade 2 tumors were a risk factor. Additionally, luminal B, HER2 overexpression, and triple-negative tumors presented increased odds of being resistant to chemotherapy relative to luminal A tumors. Thus, breast tumors with KRAS codon 12 mutations seem to present a worse prognosis. Additionally, MYC amplification may help in the identification of tumors that are sensitive to doxorubicin plus cyclophosphamide treatment. If confirmed in a large set of samples, these markers may be useful for clinical stratification and prognosis.

Interrelationship between MYC gene numerical aberrations and protein expression in individuals from northern Brazil with early gastric adenocarcinoma.

Gastric cancer is the second leading cause of death by cancer in Brazil. Early gastric cancer represents approximately 10% of gastric cancer cases in some services of Brazil, which underscores the need for early gastric cancer diagnosis that could lead to better prognosis. There are few published studies of cytogenetic alterations in early gastric cancer. To evaluate MYC copy number and its protein expression, we performed fluorescence in situ hybridization and immunohistochemical analyses in five early gastric adenocarcinomas in individuals from northern Brazil. Three signals of MYC and MYC immunoreactivity were observed in all five samples, regardless of histologic type, tumor extension, or lymph nodal status. These novel findings concerning MYC copy number alteration in early gastric cancer suggest that MYC alteration is observed in the beginning of gastric carcinogenesis and could be used as a therapeutic target.

MYC, TP53, and Chromosome 17 Copy-Number Alterations in Multiple Gastric Cancer Cell Lines and in Their Parental Primary Tumors

We evaluated whether MYC, TP53, and chromosome 17 copy-number alterations occur in ACP02, ACP03, and AGP01 gastric cancer cell lines and in their tumor counterpart. Fluorescence in situ hybridization for MYC and TP53 genes and for chromosome 17 was applied in the 6th, 12th, 60th, and 85th passages of the cell lines and in their parental primary tumors. We observed that three and four MYC signals were the most common alterations in gastric cell lines and tumors. ACP02 presented cells with two copies of chr17 and loss of one copy of TP53 more frequently than ACP03 and AGP01. Only ACP03 and AGP01 presented clonal chr17 trisomy with three or two TP53 copies. The frequency of MYC gain, TP53 loss, and chromosome 17 trisomy seems to increase in gastric cell lines compared to their parental tumors. Our findings reveal that these cell lines retain, in vitro, the genetic alterations presented in their parental primary tumors.

Cytotoxic and genotoxic monitoring of sickle cell anaemia patients treated with hydroxyurea

Very satisfactory results have been obtained with the treatment of sickle cell anaemia with hydroxyurea (HU), an antineoplastic drug. This is because it significantly increases the levels of foetal haemoglobin. Nevertheless, inadequate dosages or prolonged treatment with this pharmaceutical can provoke cytotoxicity or genotoxicity, increasing the risk of neoplasia. We monitored patients under treatment with HU for possible mutagenic effects, through cytogenetic tests (mitotic index and chromosome aberrations) for one year. Checking at two-month intervals, the cytotoxic effect was not evident. There was no evidence of genotoxicity under the conditions of our experiment. However individuals treated with HU should be constantly monitored, as an absence of genotoxicity could be transitory; the mitotic index should also be observed, as an indicator of cytotoxicity.

In vitro evaluation of the cytotoxic and genotoxic effects of artemether, an antimalarial drug, in a gastric cancer cell line (PG100).

Artemisinin is a sesquiterpene lactone endoperoxide, obtained from Artemisia annua, and extensively used as an antimalarial drug. Many studies have reported the genotoxic and cytotoxic effects of artemisinins; however, there are no studies that compare such effects between cancer cell lines and normal human cells after treatment with artemether, an artemisinin derivative. Gastric cancer is the fourth most frequent type of cancer and the second highest cause of cancer mortality worldwide. Thus, the aim of this study was to evaluate the in vitro genotoxic and cytotoxic effects induced by artemether in gastric cancer cell line (PG100) and compare them with the results obtained in human lymphocytes exposed to the same conditions. We used MTT (3‐(4,5‐methylthiazol‐2‐yl)‐2, 5‐diphenyl‐tetrazolium bromide) assay, comet assay and ethidium bromide/acridine orange viability staining to evaluate the cytotoxic and genotoxic effects of artemether in PG100. MTT assay showed a decrease in the survival percentages for both cell types treated with different concentrations of artemether (P < 0.05). PG100 also showed a significant dose‐dependent increase in DNA damage index at concentrations of 119.4 and 238.8 µg ml−1 (P < 0.05). Our results showed that artemether induced necrosis in PG100 at concentrations of 238.8 and 477.6 µg ml−1, for all the tested harvest times (P < 0.05). In lymphocytes, artemether induced both apoptosis and necrosis at concentrations of 238.8 and 477.6 µg ml−1, for all the tested harvest times (P < 0.05). In conclusion, human lymphocytes were more sensitive to the cytotoxic effects of the antimalarial drug than the gastric cancer cell line PG100. Copyright

hTERT, MYC and TP53 deregulation in gastric preneoplastic lesions

BackgroundGastric cancer is a serious public health problem in Northern Brazil and in the world due to its high incidence and mortality. Despite the severity of the disease, more research is needed to better understand the molecular events involved in this intestinal-type gastric carcinogenesis process. Since precancerous lesions precede intestinal-type gastric cancer, here, we evaluated the hTERT, MYC, and TP53 mRNA and protein expression, as well as TP33 copy number, in gastric preneoplastic lesions.MethodsWe evaluated 19 superficial gastritis, 18 atrophic gastritis, and 18 intestinal metaplasia from cancer-free individuals of Northern Brazil. Quantitative reverse transcription PCR was used to analyze the mRNA expression and immunohistochemical methods were used to assess protein immunoreactivity in tissue samples. The number of TP53 gene copies was investigated in gastric diseases by quantitative PCR.ResultsWe observed hTERT, MYC, and p53 immunoreactivity only in intestinal metaplasia samples. The immunoreactivity of these proteins was strongly associated with each other. A significantly higher MYC mRNA expression was observed in intestinal metaplasia compared to gastritis samples. Loss of TP53 was also only detected in intestinal metaplasia specimens.ConclusionsWe demonstrated that hTERT, MYC, and TP53 are deregulated in intestinal metaplasia of individuals from Northern Brazil and these alterations may facilitate tumor initiation.

Interrelationship between TP53 gene deletion, protein expression and chromosome 17 aneusomy in gastric adenocarcinoma

BackgroundThis study evaluates the existence of numerical alterations of chromosome 17 and TP53 gene deletion in gastric adenocarcinoma. The p53 protein expression was also evaluated, as well as, possible associations with clinicopathological characteristics.MethodsDual-color fluorescence in situ hybridization and immunostaining were performed in twenty gastric cancer samples of individuals from Northern Brazil.ResultsDeletion of TP53 was found in all samples. TP53 was inactivated mainly by single allelic deletion, varying to 7–39% of cells/case. Aneusomy of chromosome 17 was observed in 85% of cases. Chromosome 17 monosomy and gain were both observed in about half of cases. Cells with gain of chromosome 17 frequently presented TP53 deletion. The frequency of cells with two chr17 and one TP53 signals observed was higher in diffuse than in intestinal-type GC. Immunoreactivity of p53 was found only in intestinal-type samples. The frequency of cells with two chr17 and two TP53 signals found was higher in samples with positive p53 expression than in negative cases in intestinal-type GC.ConclusionWe suggest that TP53 deletion and chromosome 17 aneusomy is a common event in GC and other TP53 alterations, as mutation, may be implicated in the distinct carcinogenesis process of diffuse and intestinal types.

Methylation status of ANAPC1, CDKN2A and TP53 promoter genes in individuals with gastric cancer

Gastric cancer is the forth most frequent malignancy and the second most common cause of cancer death worldwide. DNA methylation is the most studied epigenetic alteration, occurring through a methyl radical addition to the cytosine base adjacent to guanine. Many tumor genes are inactivated by DNA methylation in gastric cancer. We evaluated the DNA methylation status of ANAPC1, CDKN2A and TP53 by methylation-specific PCR in 20 diffuse- and 26 intestinal-type gastric cancer samples and 20 normal gastric mucosa in individuals from Northern Brazil. All gastric cancer samples were advanced stage adenocarcinomas. Gastric samples were surgically obtained at the João de Barros Barreto University Hospital, State of Pará, and were stored at -80 degrees C before DNA extraction. Patients had never been submitted to chemotherapy or radiotherapy, nor did they have any other diagnosed cancer. None of the gastric cancer samples presented methylated DNA sequences for ANAPC1 and TP53. CDKN2A methylation was not detected in any normal gastric mucosa; however, the CDKN2A promoter was methylated in 30.4% of gastric cancer samples, with 35% methylation in diffuse-type and 26.9% in intestinal-type cancers. CDKN2A methylation was associated with the carcinogenesis process for ~30% diffuse-type and intestinal-type compared to non-neoplastic samples. Thus, ANAPC1 and TP53 methylation was probably not implicated in gastric carcinogenesis in our samples. CDKN2A can be implicated in the carcinogenesis process of only a subset of gastric neoplasias.