Oscar Tapia

Universidad de La Frontera, Ciudad Temuco, Araucanía, Chile

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Publications (42)

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    Ismael Riquelme · Oscar Tapia · Jaime A Espinoza · [...] · Juan Carlos Roa
    [Show abstract] [Hide abstract] ABSTRACT: The PI3K/AKT/mTOR pathway plays a crucial role in the regulation of multiple cellular functions including cell growth, proliferation, metabolism and angiogenesis. Emerging evidence has shown that deregulation of this pathway has a role promoting gastric cancer (GC). The aim was to assess the expression of genes involved in this pathway by qPCR in 23 tumor and 23 non-tumor gastric mucosa samples from advanced GC patients, and in AGS, MKN28 and MKN45 gastric cancer cell lines. Results showed a slight overexpression of PIK3CA, PIK3CB, AKT1, MTOR, RPS6KB1, EIF4EBP1 and EIF4E genes, and a slightly decreased PTEN and TSC1 expression. In AGS, MKN28 and MKN45 cells a significant gene overexpression of PIK3CA, PIK3CB, AKT1, MTOR, RPS6KB1 and EIF4E, and a significant repression of PTEN gene expression were observed. Immunoblotting showed that PI3K-β, AKT, p-AKT, PTEN, mTOR, p-mTOR, P70S6K1, p-P70S6K1, 4E-BP1, p-4E-BP1, eIF4E and p-eIF4E proteins were present in cell lines at different levels, confirming activation of this pathway in vitro. This is the first time this extensive panel of 9 genes within PI3K/AKT/mTOR pathway has been studied in GC to clarify the biological role of this pathway in GC and develop new strategies for this malignancy.
    Full-text Article · May 2016 · Pathology & Oncology Research
  • Oscar Tapia
    Article · Apr 2016 · Revista Chilena de Cirugia
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    Ismael Riquelme · Oscar Tapia · Pamela Leal · [...] · Juan Carlos Roa
    [Show abstract] [Hide abstract] ABSTRACT: Background: Gastric cancer (GC) is a deadly malignancy worldwide. In the past, it has been shown that cellular signaling pathway alterations play a crucial role in the development of GC. In particular, deregulation of the PI3K/AKT/mTOR pathway seems to affect multiple GC functions including growth, proliferation, metabolism, motility and angiogenesis. Targeting alterations in this pathway by microRNAs (miRNAs) represents a potential therapeutic strategy, especially in inhibitor-resistant tumors. The objective of this study was to evaluate the expression of 3 pre-selected miRNAs, miR-101-2, miR-125b-2 and miR-451a, in a series of primary GC tissues and matched non-GC tissues and in several GC-derived cell lines, and to subsequently evaluate the functional role of these miRNAs. Methods: Twenty-five primary GC samples, 25 matched non-GC samples and 3 GC-derived cell lines, i.e., AGS, MKN28 and MKN45, were included in this study. miRNA and target gene expression levels were assessed by quantitative RT-PCR and western blotting, respectively. Subsequently, cell viability, clone formation, cell death, migration and invasion assays were performed on AGS cells. Results: miR-101-2, miR-125b-2 and miR-451a were found to be down-regulated in the primary GC tissues and the GC-derived cell lines tested. MiRNA mimic transfections significantly reduced cell viability and colony formation, increased cell death and reduced cell migration and invasion in AGS cells. We also found that exogenous expression of miR-101-2, miR-125b-2 and miR-451a decreased the expression of their putative targets MTOR, PIK3CB and TSC1, respectively. Conclusions: Our expression analyses and in vitro functional assays suggest that miR-101-2, miR-125b-2 and miR-451a act as potential tumor suppressors in primary GCs as well as in GC-derived AGS cells.
    Full-text Article · Oct 2015 · Cellular Oncology
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    [Show abstract] [Hide abstract] ABSTRACT: Overexpression of Short and Raji variants of Cellular FLICE-like inhibitory protein (c-FLIP) is capable of inhibiting apoptosis, while the function of the Long isoform depends of c-FLIPL concentration in cells. The aim of this study was to determine the effects of c-FLIPL knockdown in cervical cell lines. SiHa, C-4I and C-33A cervical cancer cell lines were analyzed. c-FLIPL level expression was determined by quantitative real-time PCR and western blotting. c-FLIPL was transiently downregulated by siRNA. The effects of knockdown of c-FLIPL on cell viability, proliferation and apoptosis were assessed by comparing with scrambled siRNA-transfected cells. SiHa and C-4I c-FLIPL knockdown cells showed increased viability compared with scrambled siRNA-transfected cells (P<0.05), while C-33A cells did not show significant differences. Ki-67 and PCNA immunocytochemistry was performed to evaluate proliferation on these cervical cancer cell lines. SiHa cells with c-FLIPL knockdown showed elevated expression of Ki-67 protein compared with their scrambled counterparts (P<0.0001), while C-33A c-FLIPL knockdown cells showed a significantly lower in PCNA expression (P<0.01) compared with control. All three c-FLIP-transfected cell lines showed a higher level of apoptosis compared with their scrambled controls. Our results suggest that c-FLIPL could have effects in proliferation and apoptosis in cervical cancer cell lines.
    Full-text Article · Jun 2015 · International Journal of Morphology
  • [Show abstract] [Hide abstract] ABSTRACT: Castleman's disease is an uncommon lymphoproliferative disorder which can be unicentric or multicentric. Hialine vascular variant is the most common pathologic form, which is usually unicentric and presenting as mediastinal tumors. We report a 31-year-old female with a history of retrosternal pain. A chest CAT sean showed a tumor in the posterior mediastinum. The patient was operated and the tumor excised. The pathology report showed a Castleman's disease. No other tumors were found in the patient, who had a favorable evolution.
    Article · Jun 2014 · Revista medica de Chile
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    Full-text Article · Jun 2014 · Revista medica de Chile
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    Oscar Tapia · Ismael Riquelme · Pamela Leal · [...] · Juan Carlos Roa
    [Show abstract] [Hide abstract] ABSTRACT: Signaling pathway alterations are important in the development of gastric cancer (GC). Deregulation of the PI3K/AKT/mTOR pathway plays a crucial role in the regulation of multiple cellular functions including cell growth, proliferation, metabolism, and angiogenesis. Our goal was to assess expression of proteins involved in the PI3K/AKT/mTOR pathway by immunohistochemistry (IHC) in tumor and nontumor gastric mucosa from patients with advanced GC. We evaluated 71 tumor and 71 nontumor gastric mucosa samples from advanced GC patients, selected from Hernán Henríquez Aravena Hospital (Temuco, Chile). The targets studied were PI3K, AKT, p-AKT, PTEN, mTOR, p-mTOR, P70S6K1, p-P70S6K1, 4E-BP1, p-4E-BP1, eIF4E, and p-eIF4E. Expression data were correlated with clinicomorphological data. Descriptive and analytical statistics were used (95 % confidence interval, p < 0.05). For survival analyses, the Kaplan-Meier method and the log-rank test were used. PI3K, AKT, p-AKT, p-mTOR, p-4E-BP1, P70S6K1, p-P70S6K1, eIF-4E, and p-eIF-4E proteins were significantly overexpressed in tumor tissue. Conversely, PTEN was underexpressed in tumor tissue, notably in pT3-pT4 tumors (p = 0.02) and tumors with lymph node metastases (p < 0.001). P70S6K1 expression was associated with pT3-pT4 tumors (p = 0.03). Moreover, PI3K (p = 0.004), AKT (p = 0.01), p-AKT (p = 0.01), P70S6K1 (p = 0.04), p-P70S6K1 (p = 0.001), and eIF-4E (p = 0.004) were overexpressed in tumors with lymph node metastases. Low expression of 4E-BP1 was associated with poor overall survival (p = 0.03). Our results suggest that the PI3K/AKT/mTOR pathway is activated in GC, with overexpression in tumor tissue of most of the studied proteins (total and phosphorylated). These might be considered as target for specific targeted therapy in GC.
    Full-text Article · May 2014 · Archiv für Pathologische Anatomie und Physiologie und für Klinische Medicin
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    Ismael Riquelme · Oscar Tapia · Alejandra M. Sandoval · [...] · Juan C. Roa
    Full-text Conference Paper · May 2014
  • Conference Paper · Jan 2014
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    Priscilla Brebi · Leonel Maldonado · Maartje G Noordhuis · [...] · Rafael Guerrero-Preston
    [Show abstract] [Hide abstract] ABSTRACT: Cervical cancer is a major health concern among women in Latin America due to its high incidence and mortality. Therefore, the discovery of molecular markers for cervical cancer screening and triage is imperative. The aim of this study was to use a genome wide methylation approach to identify novel methylation biomarkers in cervical cancer. DNA from normal cervical mucosa and cervical cancer tissue samples from Chile was enriched with Methylated DNA Immunoprecipitation (MeDIP), hybridized to oligonucleotide methylation microarray and analyzed with a stringent bioinformatics pipeline to identify differentially methylated regions (DMRs) as candidate biomarkers. Quantitative Methylation Specific PCR (qMSP) was used to study promoter methylation of candidate DMRs in clinical samples from two independent cohorts. HPV detection and genotyping were performed by Reverse Line Blot analysis. Bioinformatics analysis revealed GGTLA4, FKBP6, ZNF516, SAP130, and INTS1 to be differentially methylated in cancer and normal tissues in the Discovery cohort. In the Validation cohort FKBP6 promoter methylation had 73% sensitivity and 80% specificity (AUC = 0.80). ZNF516 promoter methylation was the best biomarker, with both sensitivity and specificity of 90% (AUC = 0.92), results subsequently found in a Prevalence cohort. Together, ZNF516 and FKBP6 exhibited a sensitivity of 84% and specificity of 81%, when considering both cohorts. Our genome wide DNA methylation assessment approach (MeDIP-chip) successfully identified novel biomarkers that differentiate between cervical cancer and normal samples. These biomarkers need to be further explored in case-control and prospective cohorts to validate them as cervical cancer biomarkers.
    Full-text Article · Nov 2013 · Epigenetics: official journal of the DNA Methylation Society
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    [Show abstract] [Hide abstract] ABSTRACT: Gallbladder cancer (GBC) is a highly fatal disease with poor prognosis and few therapeutic alternatives. The molecular mechanisms involved in the pathogenesis of GBC remain poorly understood. The vascular endothelial growth factor A (VEGF-A) is a potent proangiogenic agent involved in the carcinogenesis of many human tumors and is an attractive target for cancer therapy. We characterized VEGF-A expression in advanced GBC and its relation to clinicopathologic features. VEGF-A expression was examined by immunohistochemistry in tissue microarrays containing 224 advanced gallbladder carcinomas and 39 chronic cholecystitis. The cases were classified as low or high expression to evaluate the association of VEGF-A expression level with clinicopathologic variables. The Kaplan-Meier method was used to estimate survival as a function of time, and survival differences were analyzed by the log-rank test. High expression of VEGF-A was observed in 81% (183/224) of tumors and 5.1% (2/39) of chronic cholecystitis (P<0.0001). The VEGF-A expression had a significant relationship with histologic grade and TNM stage (P<0.05). Moreover, 5-year survival analysis indicated that high expression of VEGF-A is associated with a poor prognosis in patients with advanced GBC (P=0.0116). Our results indicate that VEGF-A is highly expressed in GBC and correlates with poor prognosis, suggesting that VEGF-A expression could be used as a biomarker for predicting malignant behavior and for identifying a subset of patients who may benefit from anti-VEGF-A therapies.
    Full-text Article · Oct 2013 · Applied immunohistochemistry & molecular morphology: AIMM / official publication of the Society for Applied Immunohistochemistry
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    Dataset: Figure S2
    [Show abstract] [Hide abstract] ABSTRACT: Representative images of the effect of mTOR inhibitors on cell migration. Assays were performed using 24-well Transwell™ plates containing polycarbonate filters with an 8 μm pore size. Before seeding, G-415 and TGBC-2TKB cells were exposed to LY294002 (10 μM), rapamycin (50 nM), RAD001 (1 nM), and AZD8055 (25 nM) for 1 hour. Dimethylsulfoxide (DMSO) 0.1% was used as control. Cells were counted after 24 hours using an optic microscope. Abbreviations: DMSO, dimethyl sulfoxide; mTOR, mammalian target of rapamycin.
    Full-text Dataset · Oct 2013
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    [Show abstract] [Hide abstract] ABSTRACT: Gallbladder carcinoma is a highly malignant tumor and a public health problem in some parts of the world. It is characterized by a poor prognosis and its resistance to radio and chemotherapy. There is an urgent need to develop novel therapeutic alternatives for the treatment of gallbladder carcinoma. The mammalian target of the rapamycin (mTOR) signaling pathway is activated in about 50% of human malignancies, and its role in gallbladder carcinoma has previously been suggested. In the present study, we investigated the phosphorylation status of the mTOR substrate p70S6K in preneoplastic and neoplastic gallbladder tissues and evaluated the effect of three mTOR inhibitors on cell growth and migration in gallbladder carcinoma cell lines. Immunohistochemical staining of phospho-p70S6K was analyzed in 181 gallbladder carcinoma cases, classified according to lesion type as dysplasia, early carcinoma, or advanced carcinoma. Protein expression of AKT/mTOR members was also evaluated in eight gallbladder carcinoma cell lines by Western blot analysis. We selected two gallbladder carcinoma cell lines (G415 and TGBC-2TKB) to evaluate the effect of rapamycin, RAD001, and AZD8055 on cell viability, cell migration, and protein expression. Our results showed that phospho-p70S6K is highly expressed in dysplasia (66.7%, 12/18), early cancer (84.6%, 22/26), and advanced cancer (88.3%, 121/137). No statistical correlation was observed between phospho-p70S6K status and any clinical or pathological features, including age, gender, ethnicity, wall infiltration level, or histological differentiation (P < 0.05). In vitro treatment with rapamycin, RAD001, and AZD8055 reduced cell growth, cell migration, and phospho-p70S6K expression significantly in G-415 and TGBC-2TKB cancer cells (P < 0.001). Our findings confirm the upregulation of this signaling pathway in gallbladder carcinoma and provide a rationale for the potential use of mTOR inhibitors as a therapeutic strategy for human gallbladder carcinoma.
    Full-text Article · Oct 2013 · OncoTargets and Therapy
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    Dataset: Figure S1
    [Show abstract] [Hide abstract] ABSTRACT: Immunohistochemical staining of phospho-p70S6K in chronic cholecystitis. (A) Chronic cholecystitis negative for phospho-p70S6K immunohistochemistry. (B) Chronic cholecystitis showing positive staining of phospho-p70S6K.
    Full-text Dataset · Oct 2013
  • Juan C Roa · Oscar Tapia · Carlos Manterola · [...] · Volkan Adsay
    [Show abstract] [Hide abstract] ABSTRACT: The general impression about gallbladder carcinomas is that they are uniformly fatal; however, for the early forms, an entirely different picture indicating a very good prognosis is evolving from the high-incidence regions. We subjected 190 early gallbladder carcinomas (EGBC), defined as carcinomas confined to and above the tunica muscularis (AJCC's Tis, T1a, and T1b), and identified in cholecystectomy specimens sampled entirely according to an established protocol, to detailed analysis. Average patient age was 57.9 years (29-95). In more than half of the cases (114/190; 60 %), the tumor was inapparent by gross examination. In 81 cases (42.6 %), carcinomatous epithelium abutted the muscularis, whereas 57.4 % (n = 109) were qualified as intramucosal with no overt contiguity with muscularis. Intraepithelial extension into Rokitansky-Aschoff sinuses (RAS) was found in 34 cases (17.8 %). At the time of data analysis, 171 patients (99 %) were alive. Overall actuarial survival was 92.3 % at 5 years and 90.4 % at 10 years. The 5- and 10-year actuarial survival rates of the intramucosal group (93.2 and 92.1 %, respectively) were not statistically different from that of the muscle-abutting group (89.7 % and 88.2 % ; p = 0.334). Patients with RAS involvement had a significantly shorter survival than those without (p < 0.001). Of the 33 patients with RAS involvement, 13 (39 %) died of disease, whereas only 6 of the 154 patients (4 %) without RAS involvement died of disease. Disease-related mortality in these cases occurred relatively late (median 48 months). EGBC has a very good prognosis with a 90 % 10-year survival rate. It is seen on average in patients almost a decade younger than those with advanced cancers. RAS involvement is an independent prognostic factor, and additional surgery may have to be considered for such cases. Occasional recurrences are encountered several years later, which suggests a field-effect phenomenon and warrants long-term follow-up.
    Article · Sep 2013 · Archiv für Pathologische Anatomie und Physiologie und für Klinische Medicin
  • Article · Aug 2013 · Cancer Research
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    [Show abstract] [Hide abstract] ABSTRACT: Context.-Advanced gallbladder carcinoma (GBC) is a highly fatal disease with poor prognosis and few therapeutic alternatives. The mammalian target of rapamycin (mTOR) is a serine/threonine kinase that plays a central role in cell growth and homeostasis. Its regulation is frequently altered in various tumors and is an attractive target for cancer therapy; however, its status in GBC remains unclear. Objective.-To characterize immunohistochemical expression and prognostic significance of phospho-mTOR in advanced gallbladder carcinoma. Design.-Phospho-mTOR expression was examined by immunohistochemistry in tissue microarrays containing 128 advanced GBCs and 99 cases of chronic cholecystitis, which were divided into 2 groups according to the presence or absence of metaplasia. To evaluate the association of the level of phospho-mTOR expression with clinical variables and patient survival, the advanced GBCs were classified as having low or high expression. Statistical analysis was performed by using a significance level of P < .05, and Kaplan-Meier curves were constructed for survival analysis. Results.-Immunostaining for phospho-mTOR was positive in 82 of 128 tumors (64.1%) and in 24% of chronic cholecystitis cases (16% nonmetaplasia and 32% with metaplasia) (P < .001). Survival analysis indicated that a high phospho-mTOR immunohistochemical expression was associated with poorer prognosis in patients with advanced GBC (P = .02). Conclusions.-Metaplasia is a common finding in chronic cholecystitis and is considered a precursor lesion of dysplasia. Our results suggest that the activation of mTOR occurs very early during the development of GBC, contributing to the carcinogenesis process. Phospho-mTOR expression is correlated with poor survival, supporting the potential of mTOR for targeted therapy.
    Full-text Article · Apr 2013 · Archives of pathology & laboratory medicine
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    Carmen Gloria Ili · Priscilla Brebi · Oscar Tapia · [...] · Juan Carlos Roa
    [Show abstract] [Hide abstract] ABSTRACT: Cervical cancer is a leading cause of cancer deaths in women worldwide and infection by high-risk human papillomavirus types is a precursor event. The cellular FLICE-like inhibitory protein (c-FLIP) has been found to be overexpressed in several types of cancers and could be associated with cervical cancer progression because of its ability to inhibit the apoptotic process. To detect c-FLIP expression in cervical cancer, an immunohistochemical staining was performed, using tissue microarrays, on a series of 536 archival biopsy samples, including normal cervical tissues, low-grade and high-grade squamous intraepithelial lesions, and squamous cervical carcinomas. The epithelium in the normal cervix and low-grade squamous intraepithelial lesions mainly stained negatively for c-FLIP, whereas high-grade intraepithelial lesions and cancer samples showed an elevated expression of c-FLIP. A direct association was observed between the increasing grade of the lesion and the intensity of c-FLIP staining, in which the frequency of intense c-FLIP expression increased from 12.5% in the normal tissue to 82.1% in the cervical cancer tissue. An increased expression of c-FLIP may be an important factor in the progression of cervical cancer. This finding could aid in identifying patients with preneoplastic lesions at greater risk of developing cervical cancer. c-FLIP expression in cervical tissue may be a potential cervical cancer progression marker.
    Full-text Article · Mar 2013 · International journal of gynecological pathology: official journal of the International Society of Gynecological Pathologists
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    [Show abstract] [Hide abstract] ABSTRACT: Context: Gallbladder cancer (GBC) is an aggressive neoplasia associated with late diagnosis, unsatisfactory treatment, and poor prognosis. Molecular mechanisms involved in GBC pathogenesis remain poorly understood. Connective tissue growth factor (CTGF) is thought to play a role in the pathologic processes and is overexpressed in several human cancers, including GBC. No information is available about CTGF expression in early stages of gallbladder carcinogenesis. Objective.- To evaluate the expression level of CTGF in benign and malignant lesions of gallbladder and its correlation with clinicopathologic features and GBC prognosis. Design: Connective tissue growth factor protein was examined by immunohistochemistry on tissue microarrays containing tissue samples of chronic cholecystitis (n = 51), dysplasia (n = 15), and GBC (n = 169). The samples were scored according to intensity of staining as low/absent and high CTGF expressers. Statistical analysis was performed using the χ(2) test or Fisher exact probability test with a significance level of P < .05. Survival analysis was assessed by the Kaplan-Meier method and the log-rank test. Results: Connective tissue growth factor expression showed a progressive increase from chronic cholecystitis to dysplasia and then to early and advanced carcinoma. Immunohistochemical expression (score ≥2) was significantly higher in advanced tumors, in comparison with chronic cholecystitis (P < .001) and dysplasia (P = .03). High levels of CTGF expression correlated with better survival (P = .04). Conclusions: Our results suggest a role for CTGF in GBC progression and a positive association with better prognosis. In addition, they underscore the importance of considering the involvement of inflammation on GBC development.
    Full-text Article · Feb 2013 · Archives of pathology & laboratory medicine
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    [Show abstract] [Hide abstract] ABSTRACT: Gallbladder cancer is an infrequent neoplasia with noticeable geographical variations in its incidence around the world. In Chile, it is the main cause of death owing to cancer in women over 40 years old, with mortality rates up to 16.5 per 100,000 cases. The prognosis is poor with few therapeutic options; in advanced cases there is only a 10% survival at 5 years. Several studies mention the possible role of DNA methylation in gallbladder carcinogenesis. This epigenetic modification affects tumor suppressor genes involved in regulation pathways, cell cycle control, cell adhesion and extracellular matrix degradation, in a sequential and cumulative way. Determining DNA methylation patterns would allow them to be used as biomarkers for the early detection, diagnosis, prognosis and/or therapeutic selection in gallbladder cancer.
    Full-text Article · Jul 2012 · Clinical Epigenetics

Publication Stats

250 Citations


  • 2005-2016
    • Universidad de La Frontera
      • • Departamento de Anatomía Patológica
      • • Center of Molecular Pathology Laboratory/ Department of Pathology
      Ciudad Temuco, Araucanía, Chile